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AN
'-J
    EXPERIMENTAL AND CLINICAL

STUDY  OF  AIR-EMBOLISM.
BY
N. SENN, M.D.,
          OF MILWAUKEE, WISCONSIN,
ATTENDING SURGEON TO THE MILWAUKEE HOSPITAL; PROFESSOR OF THE PRINCIPLES AND
  PRACTICE OF SURGERY AND CLINICAL SURGERY IN THE COLLEGE OF PHYSICIANS
            AND SURGEONS, CHICAGO, ILLINOIS.
x^hgen
vs
.£-■
(ouor>)t
tfS1
        Extracted from the
Transactions of the American Surgical Association,
         Vol. III. 1885.
         PHILADELPHIA:
COLLINS, PRINTER, 7°5 JAYNE STREET.
            1885.
1/ 
Vs/G




  1285 
AN  EXPERIMENTAL AND CLINICAL STUDY OF
                  AIR-EMBOLISM.
   Sudden and unexpected death  during  an operation is a
 calamity which never fails  to strike terror to the heart  of the
 boldest surgeon.   Although death is a frequent and familiar
 visitor wherever human  beings  exist, nevertheless  its  sudden
 and unforeseen advent conveys with it more than the usual halo
 of sadness, and when such a scene transpires in  the operating
 room it  leaves  impressions which  neither time nor space can
 erase.   Disasters of this kind come without warning and usually
 at a time when least expected.  The surgeon who has the misfor-
 tune to meet with such an accident is not only destined to burden
 his memory with the unpleasant remembrances of the incident
 for the  remainder of  his days, but in addition he is often made
 an unjust object of reproach by those who are unable to  appre-
 ciate the  nature of the case. His conscience may  be relieved
 by a favorable verdict regarding his conduct and  management
 of the case before the only competent tribunal, composed of  his
 colleagues and  medical  press, but that most  uncertain of all
 things, public opinion, will, in all  probability,  be arrayed against
 him.  In one  sad moment the object of his  ambition, the ulti-
 mate aim of  his lifework  has  suffered irreparable loss.  The
 surgeon who seeks to maintain and advance the interests of  his
 profession as well as his own reputation should familiarize him-
 self with  all  the causes  and conditions which may precipitate
 such an unhappy result, with a view to adopt and  apply  timely
 prophylactic  measures.   Believing that it is good practice to
prepare for  war in time of peace,  I intend on this occasion to
call your attention to  one  of the most dreaded  and, I may add, 
6
 one of the most uncontrollable causes of sudden death ; I allude
 to air-embolism.
   After  consideration of the subject from an historical, experi-
 mental, and clinical standpoint, I shall endeavor to point out the
 conditions remote and  direct which give rise to this accident.
 The different explanations of the immediate cause of death will
 be discussed and, finally, I shall offer some practical suggestions
 relating to the prophylactic and therapeutic measures.
   By air-embolism, I understand the  presence  of free atmos-
 pheric air within the vascular system during life and in sufficient
 quantity to  give rise  to symptoms of obstruction.  It is a true
 embolism inasmuch as  the location of the volume of air which
 constitutes the  embolus is always some distance from its point
 of entrance. The presence of air in  a vessel offers the same
 mechanical  obstruction  to the flow of blood as a solid  substance,
 and gives rise to the same disturbance of circulation in  the tissues
 supplied  by the vessel.  An air-embolus differs from an  ordinary
 embolus  that, when once introduced into the circulation, it is
 capable of being broken up or divided by the blood current and
 the action of the heart, and on this account usually becomes the
 source of multiple emboli.  Pathologically it also differs from a
 solid  embolus,  inasmuch as it is more  likely to be removed  by
 absorption and  is less liable to be followed by thrombosis.  Air-
 embolism is always due to the introduction  of atmospheric  air
 into a wounded or injured vein, and, in contra-distinction to the
 ordinary  form of embolism, it is primarily most always formed
 in the right side of the  heart and in the venous system.  With
 a view to study the immediate  effects of the presence of a con-
 siderable amount of air  on the heart and the vessels, it becomes
 necessary to allude to the experiments which have been made
 where  embolism was artificially  produced by  the  introduction
 of solid substances into the circulation.

 I.  On the Immediate Cause of Death by rapidly Fatal Embolism.

   The most interesting experiments on  embolism were made
by Virchow, in 1847, and by Panum, in 1854-185 5, and although 
7
the conclusions of these experimenters are somewhat at variance,
our present knowledge on this  subject is based  upon the con-
joined labors of these distinguished writers.
  Virchow was convinced that his experiments were  conclusive
in showing that complete embolism  of the  pulmonary artery
would  invariably prove  fatal  in  a short time, while partial
obliteration of this vessel  produces either no symptoms at all or
only temporary dyspnoea, restlessness, and  a sense of oppression.
He gives the following explanation to  account for the immediate
cause of death in cases of complete obstruction in the pulmonary
artery by a large embolus.1   " The first effect  of  the pulmonary
ischsemia is the interruption  of the supply of  oxygenated blood
to the coronary arteries of the heart and the arteries of the body,
as well as the stasis of the venous blood in the right side of  the
heart, the coronary veins, and the veins throughout the body.
These conditions result in the arrest of the heart's action in  the
diastole, the tetanic contractions of the voluntary muscles,  the
retardation of respiration, the  dilatation of the pupils, the pro-
trusion of the eyeballs, etc., and very soon complete death."
  Panum, by a series of very ingenious experiments, disproved
the assertions of Virchow, that  a  lack of arterial blood in  the
coronary arteries produces  instantaneous   arrest of the heart's
action.2   In  a  rabbit, where the ventricular contractions  had
ceased for fully fifteen minutes and where  only the right auricle
continued to pulsate, he injected a warm black mass, composed
of tallow, wax, and soot, into the aorta for  the purpose of study-
ing more accurately the anatomical  relations of the coronary
arteries.  The injection  penetrated the smallest vessels.  The
right auricle continued its rhythmical movements for three and
a half hours after the injection was made, the heart  and lungs
having been removed from the body.  In a second experiment
he divided both pneumogastric nerves in a  dog, and then opened
the chest and the pericardium  and  passed  a  double  ligature
underneath the innominate artery; after tying  the upper  ligature

  1 Gesammelte Abhandlungen,  p. 297.
  2 Experimented Beitrage zur Lehre von  der Embolic   Virchow's Archiv,
xxv. p. 308. 
and drawing the lower tight, the artery was opened between them
and a silver tube  introduced and secured in the vessel with the
proximal ligature.  The silver tube was  connected with a glass
tube by interposing a piece of rubber tubing.   To the distal end
of the glass tube  another piece of rubber was attached and  all
tubes filled with oil, which was kept from leaving the tubes by a
clamp.  The aorta was compressed with  a spring forceps above
the origin of the  innominate artery  and  the same black mass
was  injected through  the tubes into the aorta.   The oil and
black  mass  entered  the  vessel,  and after  closing the aortic
valves filled the coronary arteries, which  were found completely
blocked with the foreign substance.  The movements  of the
heart  were carefully observed  before,  during, and after  the
injection was made.    Before  the  injection,  the  contractions
were  regular, 80-90 per minute; during the  injection,  on ac-
count  of  the  higher  temperature  of the  injection (45 °  C),
the contractions  became more  rapid, and  in  the left side of
the heart,  which was  distended  with  blood, they  were less
forcible, an occurrence which could be readily accounted for by
the mechanical obstruction to the outflow from the left ventricle.
All the chambers of the heart  continued to contract for five
minutes after the  injection was complete.   Six minutes after the
injection was made, the contractions of the  left auricle ceased.
The movements of the ventricles were feeble, but could be plainly
seen.   The rhythm of the ventricular contractions grew  slower
than the contractions of  the right auricle, and at the same  time
were less regular.   After twenty-five minutes the right  auricle
pulsated 48, the ventricles 24 times per minute.   Five minutes
later the pulsations  of the  auricle and ventricles were the same
in frequency.   Forty minutes after  the  injection  the ventricles
contracted 24 times per minute to 8  auricular pulsations.   Fifty
minutes after the injection the  ventricles made 23 rhythmical
movements to 3 of the auricles.   After one hour the movements
of the heart again became regular, inasmuch as the auricles and
ventricles pulsated  13 times per minute, and  in such a manner
that the movements of the ventricles followed immediately after
the contraction of the auricles and were followed by a long dias- 
9
 tolic pause.   Seventy-five minutes after the injection the move-
 ments of the left ventricle  ceased, while the right half of the
 heart contracted regularly 8 times per minute.  Two  minutes
 later the ventricle contracted only twice to 8 movements of the
 auricle.   Ninety minutes after the injection, the right  ventricle
 ceased to beat, while the right auricle continued to contract for
 6 hours and  io minutes  after the injection, making  toward the
 last  only  i  movement  per minute.  After all  pulsations  had
 ceased for a while they were renewed  by blowing upon the
 heart.  These contractions continued for seven and a half hours
 after the injection, and even after they had  ceased  for a second
 time they were again excited by mechanical irritation.   During
 this observation the heart was kept at a  temperature of 12.5 to
 13° C. under a glass  bell in which the air  was  saturated with
 moisture.  An examination of the heart showed that  the coronary
 arteries were  completely distended with the black mass, and that
 the capillary vessels and coronary veins  were blocked with oil.
 A few drops of oil, but nothing of the black  mass were found in
 the right auricle.  The aorta near the heart was filled with the
 injection material, and the aortic valves were so completely closed
 that nothing had penetrated into the ventricle.   In two other in-
 stances the coronary arteries were made impermeable in a similar
 manner, and the contractions of the heart were  temporarily ar-
 rested by electric irritation  of the pneumogastric nerves.  This
 experiment was repeated in both animals more than 20 times,
 and always with the same uniform result.   If the electric stimu-
 lation was  continued after the heart had ceased to contract, the
 movements were again excited, but this always required a con-
 tinuation of the current for  at least a minute.  If the electrodes
 were removed after the heart ceased to act, it required twenty sec-
 onds  before the contractions were re-established, the movements
 being always more rapid than before the  irritation was applied.
 From these experiments we are forced to conclude that embolism
 of the coronary arteries is insufficient to produce  instantaneous
arrest of the heart's action.   Virchow quotes  Erichsen as having
observed prompt cessation of the movements of the heart after
ligation of the coronary  arteries,  but Panum doubts the possi- 
10
bility of performing  this operation upon  the heart of a living
animal.
  The same observer studied embolism of the pulmonary artery
by injecting an emulsion of gum-arabic, in which were suspended
small pellets of black wax, into the jugular vein of a  medium-
sized dog.   Eight c. ctm. of the emulsion were injected.  All
signs of life and all reflex movements ceased three minutes after
the injection.  After death the large vessels  were tied, in order
to ascertain the exact quantity of blood contained  in each side
of the heart.  The right  side  contained 112.35 grms. of dark-
colored blood, the left contained only 6.45 grms.   In another
experiment he injected coarsely powdered charcoal in suspen-
sion into the jugular vein of a dog.  The time which elapsed
between  the  injection  and cessation of life was longer than in
the preceding case, consequently  the left  heart  contained  a
larger amount of  blood, although the  quantity was  small when
compared with that of the right side of the heart.   In all cases
of death resulting from embolism  of the pulmonary artery, the
amount of  blood  found in the  left  side of the heart is propor-
tionate to the completeness of the obstruction in the pulmonary
artery.  The left  side  of  the heart is never  found completely
empty,  as  the  labored respiratory  movements will force  the
blood, which  is present in the pulmonary vein and its branches,
into the left side of the heart.  If  instead of using small emboli
large plugs are  injected,  as  was done by Virchow, the blood
contained on the  distal side of the  obstruction will pass through
the pulmonary circulation and  reach the  left side of the heart,
consequently in such cases more blood will be found in the left
ventricle.   Panum asserts also  that the cessation of the heart's
action does not  invariably take place so early that it  can  be
considered as the primary and direct cause of death. As  a rule,
he found the heart pulsating  after  the death  struggle had been
initiated from arrest  of  innervation  from  the  cerebro-spinal
centre.  In some instances the heart continued to pulsate after
all signs of animal life emanating from the brain and spinal cord
had ceased.  Shortly after respiration was arrested the  heart did
cease to pulsate, and, as Virchow has stated,  in the diastole. 
II
  According to Panum, the  cessation or continuation  of the
heart's action exerts no influence for good or evil  in cases of
extensive embolism.   He claims that if the cessation  of the
heart's action takes place as one of the first effects after embolism
of the pulmonary  artery, as was noted in Virchow's first  case, it
must be regarded, under  certain circumstances, as being the
result of irritation of the pneumogastric nerves, so much more
so, as  the heart in the case referred  to again began to  pulsate
after the thorax was opened.  As  a rule, the heart's  action  is
arrested by distension of the right ventricle.
  Other observations tend to show  that the distension of the
right ventricle  is the cause.   The excess of carbonic acid gas
and  the diminished  supply of oxygen  must also be taken  into
account.  Other experiments have demonstrated  that carbonic
acid,  in  concentrated form,   injected into  the  heart  after its
removal from the  chest readily leads to diastolic paralysis, and
that the organ commences to beat again when exposed to air.
The arrest of the heart's action is due  to mechanical dilatation
and  the presence of an excess of carbonic acid.   The first and
most constant symptom resulting  from sudden and extensive
embolism is  a high degree of ansemia in all visible parts of the
body.  On post-mortem examination the white substance of the
brain is completely bloodless, especially if small and numerous
emboli have been  injected. This general ansemia is followed by
tetanic stretching of all extremities, involuntary discharges, and
deep, convulsive,  inspiratory movements.   Ligature of  both
carotid arteries does not produce such an  intense ischaemia of
the brain.  If the vertebral arteries are ligated at the same  time,
the tightening of the ligature  of the  second vertebral artery
produces syncope and convulsions, but the symptoms are less
intense than  after sudden, fatal embolism  of  the  pulmonary
artery.  Panum also  induced  cerebral anaemia by injecting black
pellets of wax, suspended in an emulsion, into the crural artery
of a dog, throwing the injection in a central direction through a
catheter which had been passed  into the artery near the heart,
producing thus multiple embolism in all of the smaller arteries.
The animal  lost only a few drops of  blood, and no air entered. 
12
 The  animal was taken  immediately with tetanic  convulsions,
 involuntary discharges,  and all  organs accessible to  the  eye
 presented an extremely anaemic appearance.   All reflex symp-
 toms were arrested after one to two minutes.  Two other ex-
 periments were followed  by the same results.   In  all cases the
 small wax  pellets were  found  in large number  in  the small
 vessels of the brain, as well as in all other parts of the body.
 In four other dogs cerebral embolism was avoided by introduc-
 ing the catheter only as high as the ribs, and by injecting slowly.
 During  the injection  a  peculiar  tremor was observed, which
 affected the muscles  of  the lower extremities ; this, however,
 soon ceased, and gave way to complete paralysis of both motion
 and  sensation,  as well as complete  arrest of all reflex move-
 ments.  One of the animals survived the experiment 22 hours,
 the second 9J hours, the third 6 hours, and the fourth  5 hours.
 The small vessels of the spinal  cord were found obstructed by
 the small wax  pellets, the vessels between the emboli  and  the
 heart were  much dilated, and showed  many small extravasa-
 tions. The  spinal cord was the seat of red softening, which was
 more conspicuous the longer the life  of the animal was pro-
 longed.   The spinal cord above the middle of the dorsal region
 and the brain were normal  in appearance, although scattering
 pellets were found here also.
  It will be seen that Panum, in  contra-distinction to Virchow,
 attributes the immediate cause of death in cases of rapidly fatal
 embolism to acute cerebral ansemia.
  From a study of the literature  on  air-embolism, it is  evident
that the immediate cause  of death has been assigned by different
pathologists to one of the following conditions :—
  1.  Mechanical  dilatation  of the heart and paralysis of  the
        organ in the diastole.
  2.  Acute cerebral ischsemia.
  3.  Asphyxia, resulting from mechanical obstruction  to  the
        passage of the blood through the pulmonary circulation.

  As  we shall  see further on, death from air-embolism is  not 
*3
 always produced in the same manner; the mode of dying varies
 and is modified :—
   I. By the amount of air admitted.
   2. The time which has elapsed between tfre ingress of air and
         the fatal issue.
   3. The location and  distribution of the emboli.

                  II. History of Air-Embolism.

   Surgeons and pathologists have for a long time been aware
 of the deleterious effects of free atmospheric air in the vascular
 system. The  danger attending  the  forcible insufflation of air
 into the veins of  animals was well known to many of the earlier
 physiologists.  Among the first to study the effects of the intro-
 duction of  air into veins may  be  mentioned  Redi, Wepfer,
 Camerarius, de Heyde, Harder, Bohnius, Boerhaave, Lancisi,
 Morgagni, Valsalva,  Bichat, and Nysten.  As early  as 1667
 Redi  killed animals  by  intravenous  injections  of air.  He
 observed during  his experiments that the pulse became inter-
 mittent, an occurrence which he attributed to the passage of a
 large air bubble through the heart.  His  followers who repeated
 the experiments soon discovered  that after forcible insufflation
 of air into veins the air  became diffused, inasmuch as at the
 post-mortem examinations they  found it present in the right
 auricle, the coronary vessels, and in the shape of air bubbles, in
 the smaller vessels.
   Merg made the observation  that in opening the abdomen of
 a dog and puncturing  the vena  cava above  the  origin of the
 emulgents, as the vein became emptied of blood it filled with
 air which ascended with the blood current and entered the right
 side of the heart.   Haller witnessed  the same phenomenon in
 cold-blooded animals after wounding some of the large venous
 trunks.  He has shown that it was from  this source that the air
was derived which Redi, Caldesi,  and  Morgagni had seen circu-
lating in the vessels of the same  animals.  He claimed that air
is  never seen  in  vessels when the necessary precautions  are
exercised to prevent its introduction through  a wounded vein. 
14
Nysten found,  by injecting  air slowly into a  vein, so as not to
produce the death of the animal, that the coloring of the arterial
blood  was  rendered imperfect.  He satisfied  himself that this
change was not owing to  the  embarrassment of  respiration.
Insufflation of oxygen had no effect in preventing or correcting
this  change of  color in  the  arterial  blood.  The literature on
insufflation  of air into veins is quite prolific and this subject can-
not be justly passed over without an allusion to the following
names:—
Blochmann.  Aer in venis causa mortis. Dresden, 1843.
Bouillaud. De ^introduction de l'air dans les veines.  Paris, 1838.
Gain.  De aeris ingressione in venas. Berlin, 1865.
Maguin.  Etude expe"rimentale sur  l'introduction forcee et sur l'entree spontan^e
   de l'air dans les veines.  Nancy, 1879.
Meric.  Recherches sur l'introduction de l'air et des gaz qui le constituent dans
   le systeme veineux.  Paris, 1866.
Valkenhoff. De ?eris in venas ingressu ejusque effeclu lethali.   1840.
Laborde.  Effets de l'introduction de l'air dans la circulation arterielle.  Compt.
   Rend. Soc. de Biolog.  Paris, 1873.

  These names are intimately associated with  the experimental
part of the history of air-embolism.
  It was not long after the deleterious effects of free atmospheric
air in the veins of animals had been studied experimentally before
the same symptoms were observed in man by the accidental
admission of air  into wounded veins during operations, and in
some of the  first  cases the presence of air in the veins and right
side of the heart was demonstrated by post-mortem examination.
Although a  number of honest and reliable surgeons, prominent
among them Velpeau and Fergusson,1 have denied that a suffi-
cient amount of air can be admitted through a wounded vein to
produce sudden death, this assertion  is no longer tenable in the
face  of such  a large number of well-authenticated  cases as have
been recorded in  surgical  literature by equally conscientious and
competent observers.  Since the publication of the  first well-
authenticated case  observed  by Beauchene and  described by

  1 Lettre sur l'introduction de l'air dans les veines de l'homme.  Gaz.  Med  pp
113-121.  Paris, 1838. 
'5
 Magendie the following authorities, placed in alphabetical order,
 have reported similar cases.

 Assmus.   Zur Casuistik des  Lufteindringens in  grossere Venenstamme.   Med.
     Zeitung, xi. p. 104.   Berlin, 1842.
 Amussat.  Introduction de l'air dans les veines.  Bulletin Acad, de Med., Paris,
     1836, i. pp. 894, 899;  1837-38, ii.  pp. 363, 461.
 Barlow.  An Attempt to Remove a Tumor on the  Neck; Entrance of Air in Vein;
     Sudden Death.  Med. Chir. Trans., xvi. pp. 28-35, l830.
 Chassaniol.  Observation  de I'entree de  l'air dans les veines pendant l'amputation
     du bras, clans  son articulation scapulo-humerale.   Union Med., viii. p. 428.
     Paris, 1869.
 Clemot.  Lane. Franc, torn. i. p. 357, 1830.
 Coolidge.   Case  of Sudden Death from Entrance of Air into the Jugular Vein.
     New York Med. Gazette, i. p. 305, J841-2.  Also New York Med. Journal,
     vol. ix. pp. 199-201, 1847.
 B. Cooper.  Case of Alarming Syncope from the Admission  of Air into a Vein,
     during Amputation of the Shoulder-Joint.  London Lancet,  i. pp. 448-451,
     1843-
 Cormack.   Case of Death from the Entrance of Air by a Rigid Vein in the Neck,
     opened accidentally by a Seton-Needle.   London Med. Journal, 1850.
 Delaporte.  Extirpation l'une tumeur situee au cou; introduction  de l'air dans le
     systeme vasculair.   Bulletin Acad, de Med., i. p.  132.  Paris, 1836.
 Delpech.   Mem. des hopitaux du midi.  No.  16, p. 231, 1830.
 Fischer, H.  Ueber die Gefahren des Lufteintritts  in die Venen  wahrend  einer
     Operation.   Volkmann's Sammlung klin. Vortraege. Chirurgie, No.  34.
 Gunn.  Syncope  from Entrance of Air into the Facial Vein.  New York Medical
     Journal, p. 356, 1852.
 Heckford.  Four Cases  of Entry of Air  into  the Circulation.   Medical Times and
     Gazette, i.  p. 137.   London,  1867.
 Koestlin.    Ein Fall von  Luft im Herzen.   Med.  Correspondenzblatt d. wiirtt.
     serztl. Ver., xxviii. pp. 316-321.   Stuttgart, 1857.
 De Lavacherie.   De l'opportunite d l'extraction des tumeurs du cou non  suscepti-
     bles de resolution;  reflexions sur l'introduction  de l'air  dans le cceur par des
     veines ouvertes accidentellement.   Mem. Acad. Roy. de  Med. de Beige, ii.
     pp. 305-376.   Bruxelles, 1849.
 McPharlin.  Death from Entrance of Air into the Veins  in a  Case of Compound
     Fracture.   Hosp. Gazette, iii. p. 20.  New York, 1878.
 Massart.   Etude nouvelle sur I'entree de l'air dans les veines, dans les cas  de plaie
     ou  d'operation chirurgi^ale.  Annales Soc. de Med. d'Anvers, xv. pp. 5, 57,
     113, 1854.
Mercier.   Journal des connaiss, p. 108, September, 1836.
Meyer,  F.   Case  of Injury of the Vena Jugularis Interna;  Entrance  of  Air;
     Sudden Collapse;  Recovery.  Med. Archives, iii. pp. 408-410.  St. Louis,
     1869.
Miner.  Tumor in the  Neck;  Admission of  Air into the Vein;  Death.   Buffalo
     Med.  and Surg. Journal, pp. 336-338, 1864. 
i6
 Mirault.  These.  Paris, 1832.
 Mott.  Entrance of Air into the Facial Vein.   Medico-Chir. Trans., 1830.
 Piachaud.  Mort par introduction de l'air dans une veine pendant I'ablation d'une
     tumeur du sein avec ganglions dans l'aisselle.  Echo Med., p. 768.  Neuch&t,
     1857.
 Porter.  On  the Entrance of Air into the Veins as a Cause of Death.  Journal
     American Med. Asso , iii. No. 20.
 Rauch.  Lufteintritt in einen verletzten grosseren Halsvenenast und seine Folgen.
     Oest. Med. Wochenschr., pp. 199-201.  Wien, 1845.
 Roux.  Journ. Hebdom., ii. p. 64, 1833.
 Schmid.  Das Eindringen von  Luft in  eine Vene wahrend einer Operation am
     Halse.   Corresp.  blatt d. wiiitt. aizt. Ver., xxi. p. 53.   Stuttgart, 1851.
 Schweickhart.  Eindringen von Luft in die  Venen; Tod durch Gehirnschlag.
     Mitth. des badischen arzt. Ver., vi. pp.  69-71.  Karlsruhe, 1852.
 Smith, R. W. Abscess behind the Pharynx; Entrance of Air into Veins. Dublin
     Quarterly Journal Med.  Sciences, xxv. p 497, 1844.
 Tadlock.  Entrance of Air into Divided Internal Jugular Vein; Ligation; Re-
     covery.  American Journal of Medical  Sciences, p. 280, 1875.
 Ulrich.  Tod durch Eintritt von Luft in die  Venen.  Med.  Zeitschrift des Vereins
     fur Heilkunde, p.  132, November, 1834.
 Warren, J. C.  Two Cases of Accidents from Admission  of Air into the Veins
     during Surgical Operations.  American  Journal of  Medical Sciences, pp.
     545-548, 1832.
 Warren, J. M.  Tumor connected with the  Sartorins Muscle; Secondary Cancer
     of Breast; Operation;  Entrance of Air into the Vein; Recovery.  Surgical
     Observations, p. 529.  Boston, 1867.
 Wattmann.   Prager Viertelj., ii. p. 191, 1844.

   This  list is, of  course,  not complete, nor does it  represent all
 cases of accidental introduction of air during operations; but the
 names  which  are quoted  ought   to  be  accepted  as sufficient
 guarantee  by the most skeptical that  the fear of this accident is
 not  a myth but a reality substantiated by many a sad experience.


               III.  Intravenous Production of Air.

   Spontaneous  production  of air  within  the bloodvessels  of
recently deceased  persons has been repeatedly observed, and to
it  has been assigned  one  of the causes of sudden death.  That
the  air thus produced is a direct product from the blood  appears
to be negatived by the fact that its occurrence has usually been
traced in connection with sudden and  exhaustive hemorrhages.
It is, in  fact,  in  persons who have  died  from  hemorrhage, that 
17
 air has been found in greatest abundance in the veins.  Lieutand1
 reports the case of a girl who died suddenly in a state of syncope,
 after having  been repeatedly bled, and in whom  the cerebral
 veins  and choroid plexus were found  impacted with air.  M.
 Rerolle2 has published several cases of the kind, where profuse
 hemorrhage had  existed; in  one of  fatal epistaxis, the  heart,
 arteries, and veins contained large quantities of air.  Dr. Graves
 has noticed emphysema of the abdominal parietes in a sufferer
 from repeated attacks of epistaxis.  M. Rerolle conjectures that,
 in such cases, air is absorbed  by the radicles of the pulmonary
 veins—the air would have no claim to be considered adventitious.3
 It  is,  however, more logical  to assume  that, inasmuch as in
 almost all cases the supposed intravenous origin of air took
 place consequent upon severe  losses of  blood, hence likewise in
 connection with loss of continuity of the  vascular system, that,
 owing to  the sudden  loss of intravascular pressure, the air may
 have been aspirated through the openings of some  of the  bleed-
 ing vessels.   The quantity of  air found in  these instances has
 been so small that it  has been  impossible to make a chemical
 examination to  determine its identity with atmospheric air.  In
 cases where air was found in blood  without loss  of continuity of
 the vessels, it is not  impossible  that  the supposed air was not
 atmospheric air, but a gaseous product liberated from the blood
 or generated  in the  tissues, producing  a  gas-embolism which
 interferes  with the function of  circulation in a similar manner as
 when the  obstruction is caused by atmospheric air.

 IV. Effect of the Heart and Respiration on the Venous Circulation.

  As the  state of the intravenous blood pressure constitutes the
 most important  element both in the prevention and causation of
aspiration  of air into veins, this subject must be briefly alluded
to in order to determine  the conditions which act  as  exciting
causes.  For the most reliable and  comprehensive information

  i Hist. Anat., Med. Obs. 55.            * These de Paris, No. 129, 1832.
  3 Todd's Cyclopaedia of An. and Physiol., vol. iv. part i. p. 145.
       2 
i8
on this subject we are indebted to Jacobson.1  The observations
were made on sheep.  To determine the  effect  of  the heart's
action  upon  the venous  circulation  he measured  the blood-
pressure  in veins with the  manometre.   These  measurements
were made on veins in close proximity to the heart, as the lower
portion of the jugular and subclavian, as all attempts to approach
nearer  the heart seriously  impaired  the normal physiological
conditions  of the respiratory and  circulatory  organs.   This
measurement gave the following results :—
In the left vena anonyma
"  " right "  jugularis
"  " right " . subclavia
"  " left  "  jugularis
u  " left  "  subclavia
— o.i mm. H§
+ 0.2  "
— o.i  "   "
— o.i  "
— 0.6  "   "
  The following are his observations on some of the more distal
veins in the same animal:—
. -f- 3.0 mm.		Hg.
• +5-2	i<	"
• +4-1	(<	a
. 4-9.0	ii	"
. +11.4	!<	"
In the external facial
"  " internal  "
"  " brachial
" a branch of the same
" the crural vein
  The experiments of Ludwig and Mogk, although made in a
similar manner, led to more variable and inconstant results; at
one time  they found the blood-pressure in  the crural vein 6.8
mm. Hg., while on another occasion under similar circumstances
it measured in the same vein only 1.9 mm. Hg.   Donders ex-
plains this want of uniformity to  the respiratory movements of
the chest, believing that the aspiratory movements of the chest
affect the  venous  circulation more than the vis a tergo from the
capillary  system.  Poisenille  claimed  that in his  experiments
the manometre was affected  by  the respiratory movements of
the chest  only when it was inserted into veins in close proximity
to the  heart, as in the lower portion of the jugular and  the ex-
ternal  iliac  veins, while in  more distant  veins the column of
  1 Dr.  Heinrich Jacobson.  Ueber Blutbewegung in den Venen.  Virchow's
Archiv, xxxvi. p. 80. 
19
 mercury  was  not affected  by  the movements of  the  chest.
 Volkmann obtained the following measurements:—
        In the facial vein of a goat .    .    .    .  41  mm. Hg.
        "  "  jugular vein of a goat   .    .      18   "   "
        "  "  metatarsal vein of a calf .    .      27   "   "
        "  "  jugular vein of a calf   .    .    .  21.5 "   "
        " a subcutaneous vein of the neck of a horse 44   "   "
        " the jugular vein of a horse  .    .    .  21.5 "   "

   Magendie found the blood-pressure  in  the external jugular
 vein  of a dog 18 mm.  Hg., and  in the  crural vein 50  mm.,
 although the  measurements  of the intravenous blood-pressure
 taken by different observers are at great variance, and although
 their figures are indicative of the opinions  held  by the different
 experimenters as to the effect of respiration  upon the return of
 venous blood, yet they all agree in locating the minimum degree
 of  intravenous  pressure  in the veins  nearest the  heart.  The
 effect of  respiration  on the venous circulation was  thoroughly
 investigated by Magendie.   He introduced an elastic tube into
 the internal jugular vein, and observed that blood would escape
 only  during  expiration.  The same experiment was made  on
 the crural vein by directing the tube towards the heart, followed
 by the  same result.   The suction force  exerted  during inspira-
 tion was sufficient to counter-balance the auricular contractions.
 In  making these experiments air was frequently drawn into the
 heart during forcible  inspiration.  Barry introduced through the
jugular vein of a horse a'bent tube of glass, one extremity being
passed  into the right cavity of  the  heart, or the vena cava, and
the other  into a vessel containing  a colored fluid.   He found
that with each  act of inspiration the liquid rose in the  tube,
demonstrating the effect  of a notable suction force.   He found
that this suction force was increased by preventing the entrance
of air into the chest by the trachea.   He was of the opinion that
this force from the chest was  exerted not only in the large veins
near the heart, but throughout the entire venous system.
  Schweinburg1 has  studied  the effect of respiration on the

  ' Die Bedeutung der Zwerchfellcontractionen  fuer  die respirat. Blutschwan-
kungen.  Du Bois-Reymond's Archiv, 1881, p. 475. 
20
circulation by producing paralysis of the diaphragm  by section
of  the phrenic  nerves.  He  states that when  diaphragmatic
respiration has  been artificially arrested, the difference of blood
pressure observed during respiration ceases entirely or nearly so.
From  this  he  concludes that  the action   of  the diaphragm
causes to a certain extent these differences.   Even after opening
the abdominal  cavity the difference in blood-pressure  is very
slight.  As  the principal cause  in  abolishing the effect of res-
piration upon the circulation he  looks  upon the compression of
the abdominal vessels during inspiration, causing the  increase of
blood  pressure  during  inspiration  and its diminution during
expiration by diminishing intra-abdominal compression.  If the
jugular vein  in  an animal is  exposed,  direct observations show
conclusively  that  the direct influence  of inspiration  cannot be
felt much beyond these vessels.   The  flaccidity of the walls of
the veins will not permit the extended action of any  suction
force, but the flow of blood in the distant veins is accelerated by
the intermittent emptying of the veins by  the  respiratory act.
Barry  and Donders  ascribe  to the  aspiratory function of the
chest,  the principal motor  in  the  return of the venous  blood.
Donders estimated the aspiratory force  of the inspiratory move-
ments  of  the chest at 7 mm.   Clinical observation and experi-
mental  research have   established  the  fact  that the  venous
circulation is directly influenced by respiration within a certain
area, and that aspiration of air  in  the  majority of cases takes
place in those veins  thus affected,  thus constituting  the justly
and much dreaded "danger-zone."  Instead of speaking of the
effect of respirat on on veins as a cause of aspiration of air, some
authors speak of the vein pulse, and limit  the danger-zone to
such  veins  which  pulsate.  Under certain  circumstances the
pulsations of the arteries are communicated directly to the veins
through the capillaries.   In such instances  it is  necessary that
the arterioles are relaxed, as has been ascertained by Bernard in
observing the circulation in  glands during  their  physiological
activity.  If a vein be opened in a gland during its physiological
activity, the blood retains partly its arterial hue and  escapes in
intermittent jets, as from a divided artery.  According to recent 
21
 physiological  investigations  veins continue  to  pulsate inde-
 pendently of the arterial system and the cerebro-spinal centres.
 Luchsinger1  examined  the  venous  pulsation in the  wings of
 bats.   Contrary to Schiff's observations he found it independent
 of the central nervous system.  Division of the brachial flexus
 and separation of all tissue connections between hand and body,
 with the exception of the vessels, did not arrest it.  If artificial
 circulation  was  established  in  the  organ  after amputation
 rhythmic venous contractions would  be seen even twenty hours
 after  death.   Intravenous pressure  was found to  be  of great
 importance  in these  experiments ; as soon  as it was increased
 the vein began to pulsate.   The seat  of these rhythmic con-
 tractions Luchsinger  placed in the walls of the vessels,  or rather
 in their muscular structures.  They are probably regulated by
 the central  nervous  system.  Slight increase of  warmth and
 electric  tetanization accelerate the contractions.  High  tempera-
 ture causes diastolic stasis.  Nitrite of amyl increases the  pulsat-
 ing only to arrest it later.  Schiff has since  satisfied himself
 that  these pulsations continue after division of  the  brachial
 plexus  and  ligature  of the vessels, and even  in the  veins  in
 detached pieces of the bat's wing.
   Brunton2 has made the  same observations on man in regard
 to the effect of increased intravascular pressure in producing
 venous pulsations  in  the larger veins.   He finds that pulsation
 of the jugular  vein is  sometimes confined  to one side, the left
 one.   In one of his cases the jugular  on the left side was much
 more distended than the right jugular, the distension increasing
 whenever the  vein was  compressed just above the  clavicle.
 Whenever this compression was repeated in the rhythm of the
 pulse, the increase and decrease of the blood  in the vein  assumed
 the character of pulsation, and  for this reason the author has
 arrived  at the conclusion that the  venous pulsation  in such
 instances is caused by compression of the vena anonyma by the
 aorta.  All cases of  unilateral jugular  pulsation  observed  by

  i Vou den Venenherzen in der Flughaut  der  Fledermaase.  Pflueger's Archiv,
 1881, vol.  xxvi.
  z On Pulsations in the Jugulars and other Veins. Medical Press and Circular,
July 2, 1879. 
22
Brunton occurred  in  ansemic  women.  In  one of  these  the
pulsation took place only while the patient was affected by some
emotional excitement, in another only during expiration.   In
rabbits  the author has  repeatedly  observed rhythmical con-
tractions of the pulmonary veins, the vena cava inferior, and the
portal vein, occurring immediately after the death of the animals.
These pulsations were present  either after complete cessation of
the heart's action, and sometimes even before death, and, as the
pulsations  were more frequent than the heart's  action, it was
plain that they occurred independently from any contraction of
that organ.   In consequence of long-continued  pressure on a
vein the author  has seen tonic contractions to take place, espe-
cially in smaller veins, and this may explain the cause of some of
the irregularities of the circulation and subsequent transudation.
   Riegel1 has made vein pulsation a  special subject of investi-
gation,  and  as  the  result of his researches  he has come to the
following conclusions:   I.  There exists in the normal condition
a  pulsation of the jugular vein.  2.  This  normal pulsation  is
always  anadicrotic, i. e., its  wave rises  in two distinct intervals.
The anadicrotic wave corresponds, in contra-distinction to the
pulsation  of the carotids, to the disatole of the heart.  The short
catacrotic line or wave corresponds to  the systole, the anacrotic
to the diastole of the  heart.  Synchronous with the systole, the
contents of the vein are emptied into the heart, while during the
diastole stasis takes place in the veins.
   King,2 in his  interesting essay "On the Safety-valve Function
in the Right Ventricle of the Human Heart," demonstrates the
existence of venous  pulsations  in the veins of the  hand, the
median veins of the forehead, and the external jugular which he
observed  after  a full meal.  The pulsations were made plainly
visible  by taking  a delicate thread  of sealing wax  about two
inches  in length,  one end of which  was fixed across the vein
with a  little tallow  so  as to make a  long and  excessively light
lever, capable of indicating  a very slight movement in the vessel.

   1 Zur  Kenntniss  von  dem Verhalten  des Venensystems unter normalen  und
pathologischen Verhseltnissen.  Berl. Klin. Wochenschrift, 1881, No. 18.
   2 Guy's Hospital  Reports, 1837, p. 108. 
                             23

The movements of the lever produced by the vein pulse corres-
ponded in frequency with the pulsations of the arteries in the
same  vicinity, but did  not  correspond  in time as the  venous
pulse  followed the  arterial systole,  showing  conclusively that
it  was  not  due to  the impulse  of  an adjacent  artery.   The
pulsations could only be caused by the arterial wave  being
continued to the veins through the capillary vessels.   In certain
pathological conditions  independently of valvular lesion of the
heart  he noted  a marked  increase in  the  venous  pulsations
in the dorsal veins of the hand and other vessels distant from
the heart.   The subject of the vein pulse  affords  an inter-
esting  topic in  physiology, but in connection with  this paper
it  is only mentioned in order  to show that the intravenous
tension is only  slightly affected  by it, and consequently it can
exert no direct influence in  causing aspiration of air  into veins.
The venous pulsations which directly influence the return of the
venous blood to the right side of the heart occur synchronously
with the movements of respiration and are observed only in the
veins which are  in close proximity to the heart, and in venous
channels with firm unyielding walls.  The introduction of air
can only follow in wounds of vessels where the intravascular
pressure is  subjected to  great variations either  from  normal
anatomico-physiological conditions or the result of pathological
alterations.  All causes which prevent a prompt collapse of the
walls  of a wounded  vein must be  considered as predisposing
causes, while all conditions which tend to produce a  vacuum in
the wounded vein act as determining causes.  The  location of
the former  corresponds to the point of  injury, while the  latter
are always  represented by the aspiratory action of the  chest
during inspiration.

   V.  Aspiration of Air into the Superior Longitudinal Sinus.

   Nearly all of the older physiologists were of the opinion that
aspiration  of  air into veins could  only take place  in vessels
which  were in close proximity to the heart and within  reach of
the venous  pulse.  Mery claimed that  the  effect of  thoracic 
                              24
 aspiration on the venous circulation extends to the  sinuses of
 the dura mater and the venous  channels in the diploe of the
 cranial bones.   Bernard was  aware that air might enter the
 sinuses in case these structures were wounded, as this accident
 occurred a number of times in his experiments on animals where
 the superior longitudinal sinus was opened  for other purposes.
 He believed that the air, after entering  the sinus  reaches the
 heart through the vertebral veins and the vena azygos.   Death
 in  such  instances took  place  in eighteen minutes, while forty-
 five minutes were required if  death  resulted from  hemorrhage
 alone.
   Volkmann's case,  reported  in another  part  of this  paper,
 demonstrates to a certainty that death may be caused  by the
 entrance of air through a wound of the longitudinal sinus, and,
 although  this is the  only authenticated  case on record, similar
 cases have undoubtedly occurred before, but the real cause of
 death was not recognized, and  the fatal result was attributed to
 some other source.  This subject of aspiration  of air into the
 longitudinal sinus was made the object of experimental  inquiry
 by  Genzmer, one of Volkmann's  assistants.1
  The experiments were made on dogs, as this vessel in rabbits
 was found too small for  the operation.  Nine experiments were
 made.  The animals were made partially insensible by morphine
 injections.  The  skull was  exposed  by an incision which was
 carried from the occipital bone  to  the forehead;  with a small
 straight chisel, a section of bone about 6 cm. square was mapped
 out  by  cutting  through  the external table, anteriorly to  the
 prominentia occipitalis externa,  and which was completely de-
tached with a hollow  chisel.  The dura mater having  thus been
freely exposed the posterior portion of the  longitudinal sinus,
which was about 2 mm. in width, was made  accessible about its
 middle.   Between two small hooks  the sinus was made tense
and divided  transversely, carefully guarding against  injury to
the subarachnoidean  space.  In  some  of the experiments  the

  1 Exstirpation eines faustgrossen Fungus durse matris, todtlich verlaufen durch
Lufteintritt in den geoffneten Sinus longitudinalis.  Verh. d. deutschen Gesellschaft
f. Chirurgie, vol. vi. p. 32. 
25
 wound was kept patent by making traction on its margins with
 the hooks, in others this precaution  was unnecessary as the
 edges of the wound retracted sufficiently to  keep it open.   For
 several minutes after incision the  bleeding continued profusely;
 the blood was quite red and escaped with some degree of force,
 the pulsations being  plainly visible and synchronous with the
 heart's action.  The stream was also perceptibly increased  and
 diminished with the respiratory movements of the chest.  After
 a few minutes had elapsed the hemorrhage became less profuse.
 In case the animal died, the heart and lungs were removed, after
 carefully tying the large vessels so as  to prevent the escape of
 air  from the heart.   To secure accuracy  in ascertaining  the
 presence of air in  the heart, this organ was opened under water
 when the rising bubbles would indicate its presence.   In three
 cases, in two of them  the  animal breathed  through  a tracheal
 canula, the double rhythm in  the blood column was lost soon
 after the sinus was opened, and the blood continued to flow until
 the animal died, which was  usually the case after  thirty-five,
 forty, and fifty-three minutes, the stream from the peripheral  end
 of the sinus growing constantly less during this time.   In all of
 these  cases the central end  of the sinus was completely filled
 with a thrombus, and  no air was found in  the heart.  In  two
 other cases the double rhythm continued until life was extinct,
 which was the case after twelve and nineteen minutes.  After
 the first two or three minutes the bleeding  diminished, and, by
 removing the blood from time to time with a sponge, it could be
 seen how air was aspirated  during inspiration through the gap-
 ing wound.   During forcible expiration, or on compressing  the
 chest, air bubbles escaped with the blood from the wound, from
 the proximal end  of the sinus.  As the bleeding diminished air
 aspiration became  more copious and more frequent.  An exami-
 nation of the cadavers of these animals revealed that the right
 side of the heart contained air and spumous blood.  In the next
 two cases artificial  dyspnoea was produced, in one instance by
 dividing both  pneumogastric nerves, in the other by closing  the
 tracheal  canula through which the animal was breathing.  In
the first case air entered  early and the  animal died  in sixteen 
26
minutes; in the second case air entered freely during the forcible
inspiratory efforts; the animal died in twenty-four minutes.   In
both of these cases air was found in the right side of the heart
and in the subpleural vessels.  In the last two experiments the
animals were killed fifteen and sixty minutes after the sinus was
opened, by puncturing the brain with a needle.  In the first case
a considerable amount of air was found in the right side of the
heart, and in the second case the amount of air contained in the
right  side of the  heart was less, the apparent difference being
due to the presence of a thrombus in the central end of the sinus
in the last case which prevented  further ingress of air.
  In recapitulation it may be stated that in  six out of nine ex-
periments air entered the  longitudinal sinus, thus proving con-
clusively that wounds of this great reservoir  of venous blood are
not only dangerous  from the loss of blood,  thrombosis, and
inflammation, but may also  become the direct cause of sudden
death by admitting air into the venous circulation.

                      VI. Experiments.

  These experiments were made by the writer  for the purpose
of ascertaining more  fully the conditions which  determine the
entrance of air into  a wounded  longitudinal sinus, and, at the
same time, to obtain  reliable information concerning the prophy-
lactic measures  as well as  to determine the  best  methods of
arresting hemorrhage in wounds of this vessel.  All operations
were made under antiseptic precautions; when not specified, no
ansesthetic was used.   The field of operation was cleanly shaved,
and the surface thoroughly disinfected with a five per cent, solu-
tion of carbolic acid; during the  operations, frequent use was
made of the irrigator, using a warm two per  cent, solution of the
same antiseptic.   When the animal survived the  operation, the
wound was closed with continued catgut sutures, dressed with
iodoform, and a compress of salicylated cotton  retained by a
roller bandage.  The operation consisted in  making a longitudi-
nal incision in the median line of the skull, reaching  from the
external occipital  protuberance to near the  upper extremity of 
27
the frontal  sinuses.  The soft  parts with  the periosteum were
separated and reflected on each  side so as to lay bare the bone
over a sufficiently large area for the ready use of the bone-cut-
ting instruments.   A medium-sized trephine was applied over
the middle of the longitudinal sinus, and the button of the bone
carefully removed so as to prevent injury of the underlying ves-
sel.   The enlargement of the circular  aperture  was  effected
with a hollow chisel and Luer's bone-forceps.   The  opening in
the bone was made of an oval or oblong shape with the longest
diameter  parallel  to the sinus, in  order  to  bring into  view  a
large extent of the vessel  with a minimum destruction of  the
cranial vault.

  Experiment No. i.—Small Skye terrier, weight 12 pounds. Ether
used as an anaesthetic.   Longitudinal sinus laid bare to the extent
of  one  and  one half  inches  by an oval opening  in  the  skull.
Copious hemorrhage from a vein leading into sinus which was ar-
rested after ligature.  Two catgut ligatures were placed underneath
the sinus about one-half inch apart, and  the vessel  cut transversely
between  them.  The bleeding was very copious,  the blood escap-
ing in jets synchronous with  the heart's  impulse, the flow  was  also
distinctly increased  and  diminished  by  the respiratory movements
of the chest.   During inspiration the stream was  diminished while
expiration was  always  attended  by a decided increase  in the force
of the  jet and the amount of bleeding.   No air was seen to enter,
although the  hemorrhage had been very  profuse and continuous for
a considerable length of time.   As it was intended by  this experi-
ment to prove that  sudden obliteration  of the longitudinal sinus is
not incompatible with life, the distal  ligature was tied with the effect
of nearly but not  completely arresting   the hemorrhage,  as some
blood escaped from the proximal end of  the vessel.   It was now ex-
pected that  air would be more prone to enter through the gaping
wound in the sinus as the blood pressure from the distal end of the
vessel had been arrested by the ligature,  but as this accident did not
take place after a few minutes the second ligature was tied, and the
wound in the skin united with the continued catgut suture,  and  the
antiseptic  compress applied.   The animal  showed no other symp-
toms except great prostration from the sudden and profuse loss of
blood.   After an hour it rallied  and apparently was in full posses- 
28
sion of all  its special senses, and was able to walk  about as usual.
The next day  it manifested  a ravenous appetite, and, during the
whole time it was kept under  observation, it showed no signs of ill-
ness or discomfort.   The wound united by primary union, the skull
showing the oblong bony defect at the site of the operation through
which the pulsations of the brain could be  distinctly seen  and felt.
Unfortunately the animal ran away after  complete  recovery had
taken place  and deprived me of the opportunity to study by post-
mortem examination the  local effect on the intracranial circulation
by the operation.  This experiment tends to prove  that ligature of
the longitudinal sinus can be  performed without seriously compro-
mising the  functions of the brain, and that in certain  well-defined
instances this procedure  might be  resorted to in practice  with  a
view of preventing or arresting hemorrhage from, and  the entrance
of air into, this vessel, in  intentional or  accidental wounds of the
sinus.

  Experiment No. 2.—Small  tan cur,  weight  10 pounds.   Partial
ether anaesthesia.   Longitudinal  sinus opened by two transverse
incisions in  close proximity;  hemorrhage alarming, at first in  jets,
and, as  the  bleeding diminished, in a more continuous flow.  At
first  the blood was bright  red, but as respiration became impaired,
it grew darker in color.   Dilating forceps were introduced into the
proximal wound, the hemorrhage continued, but  no air entered as
long as  the animal was  in a  lying  position, but  as the respiration
became  more  irregular  and   superficial  artificial respiration was
resorted to, and the head  placed in an elevated  position, whereupon
the heart suddenly ceased  to pulsate, and, upon applying the ear to
the precordial  region, a few irregular and very feeble contractions
were heard, attended by a distinct churning sound, when the animal
suddenly expired.   Before death electricity was used with  the effect
of improving the respirations, but it had no effect whatever upon
the action of the heart.   Death took place about three-quarters of
an hour  after the sinus was opened.   At  the examination, imme-
diately after  death, all the tissues  and organs were  found in an
exsanguinated condition.   All the vessels leading to and  from the
heart were carefully tied, and the organ removed.  On being placed
in water it floated  like a cork; the  right  auricle and ventricle were
dilated,  and on being opened under water  bubbles of air  and only
a very slight amount of spumous blood escaped.   The pulmonary 
29
 artery was also  distended with air.   The  left ventricle was almost
 completely  empty.   In this  instance the animal  almost bled to
 death  from the wounds in the longitudinal sinus, and  yet no air
 entered, although  the wound was kept patent with a pair of forceps.
 The entrance of air was caused  by the elevation of the  head and
 the  forcible movements of  the  chest during  the  performance of
 artificial respiration.   To judge from the amount of air found in the
 right side of the  heart and its  effects, the air must have entered
 quickly and  in considerable quantity, distending at once the  right
 side of the heart to such an extent as to paralyze the muscles of the
 heart in the diastole,  after a few feeble attempts to force  it from the
 right chambers.   I believe, if the animal had been left in the  lying
 position,  and the  head dependent,  that  death would have taken
 place from  hemorrhage, as the blood which was draining through
 the sinus prevented the entrance  of air, but as soon as the head was
 raised,  the contents of the sinus  by gravitation flowed towards the
 heart, and air entered  with  it to fill the vacuum which  was being
 prepared by the  diminished  blood  supply to the brain, and the
 acceleration of venous return, as well as the  increased aspiration of
 the  chest, which  was brought about by the attempts at artificial
 respiration.

   Experiment No. 3.—Horse, about 12 years old.  Partial chloro-
 form anaesthesia.  Animal kept lying on the ground, head even with
 the body.  Longitudinal sinus exposed for about two inches and
 incised  longitudinally one inch   Hemorrhage very profuse; blood
 at first bright red,  gradually growing darker in color;  double  wave
 well marked.  After about three  quarts of blood had been lost, and
 the hemorrhage still  continuing at  the same rate, and  not being
 readily  controlled  by the ordinary compression, it  was decided to
 implant an aseptic sponge  into the sinus.   This was done, and the
 external wound united over it  by  the continuous suture.  No air was
 seen to enter the  wound, and auscultation over the heart revealed
 no abnormal sounds.  During the operation of chiselling, the apices
 of the frontal sinuses were opened, which led to the fear that infec-
 tion  of  the wound would subsequently take place from this source.
This expectation was realized.  The animal rallied soon after the
operation, and appeared to be quite well for three days subsequently,
grazing in the pasture with  other horses.   On  the  morning of the
fourth day it was found dead.   Examination of the cadaver showed 
30
that the proximal end of the sinus was closed by a thrombus firmly
adherent to the walls of the vessels and the implanted sponge, but
about the distal end  of  the sponge, at a point which corresponded
to the opening in the frontal sinuses, the brain and meninges showed
all the appearances of acute septic inflammation.   If infection had
not taken place the aseptic sponge would have fulfilled all the pur-
poses for which it was intended—arrest of hemorrhage and oblite-
ration of the sinus.  It  seems to me that in cases of uncontrollable
hemorrhage from accessible venous sinuses, the implantation of an
aseptic sponge would prove  a safe and efficient measure  against
hemorrhage, and would offer no obstacle against obtaining primary
union and definitive  closure of  the vessel, as during "the process of
granulation the sponge disappears by absorption.

   Experiment No. 4.—Horse, 14  years old, in good condition.
This experiment was made for the  purpose of confirming the sus-
picions already gained  that the force of gravitation constitutes the
most important factor in determining the admission of air into an
open  sinus of  the dura mater;  consequently no  anaesthetic was
given, but the animal was firmly held  by a bit,  and the operation
was performed, without  any  difficulty, while the animal was in  a
standing  position with the  head elevated.  With  the  trephine and
chisel an oval opening,  about  two and  a half inches in extent, was
made over the longitudinal sinus.  After all oozing had ceased, and
the sinus being fully in view, its anterior wall was divided completely
in a transverse direction.  The edges of the wound immediately
retracted, forming a diamond-shaped opening through which blood
escaped in moderate force, but not nearly as copiously as on previ-
ous occasions when the animals were in the lying position.  During
the first inspiration after incision air entered with a loud gurgling
or lapping sound, and  on  applying the  ear over the apex of the
heart  a loud churning  sound was heard  synchronous with  the
movements of the heart.  During expiration  air-bubbles were seen
to escape from the proximal end of  the sinus.  As soon as the head
was depressed  the hemonhage greatly increased, but air  never
entered  in  this position; but as soon as the head was elevated
hemorrhage either ceased entirely or was at least greatly diminished,
but air was  sure  to  enter during  inspiration.  These manoeuvres
were repeated a number of times, and always with the same results.
As the amount of air which was  aspirated  increased, the respirations 
3i
became more labored, and signs of cyanosis became apparent.  An
attempt was now made to close the wound  in the sinus by sutures,
and in this way arrest the hemorrhage.  Three catgut sutures were
passed through  both edges of the wound, but  on  attempting to
approximate its margins every one of them  tore through the tissues
before the parts were in apposition, proving conclusively that trans-
verse  wounds of the  longitudinal sinus cannot be sutured, owing to
the unyielding nature of the tissues.   The external wound was  com-
pletely closed  by the continuous suture,  and a firm graduated  anti-
septic compress controlled the bleeding.  During the whole time of
the operation, which lasted over an hour, some one of the bystanders
listened to the heart's  action, and the loud splashing or churning
sounds were constantly heard.  When  the animal was released  it
commenced grazing in the pasture, and appeared as well as before
the operation.   The  heart was examined at  intervals  of thirty
minutes, and  the abnormal sounds grew more feeble, and after an
hour had entirely disappeared.   The sound produced by the enter-
ing air, I have  described as  lapping, resembling very much the
sound produced by  the lapping of a dog or cat; the best possible
word  for  this  sound  is the  German expression "schluerfend."
When air enters through a wound of  the longitudinal  sinus this
sound is characteristic, and is always the  same, and,  in case the
animal operated upon is a horse, it  is sufficiently loud  to be heard
at some distance.   Experiments have shown that horses are  most
tolerant to the presence of air  in veins, on account of the  unusual
development of the right ventricle, which  has sufficient power to
force  the  air  through  the pulmonary circulation, and  this experi-
ment  would certainly tend to corroborate this observation, as air in
large  quantities  was aspirated  at least  a  dozen  times during the
operation, and that most of it entered the  right side of the heart,
and was not returned is evident from the persistence of the  sounds,
due to the presence of air for a period of two hours, and yet,  aside
from a certain degree of embarrassment of respiration, the animal
suffered no inconvenience.  The wound healed  by primary union.
The defect in the skull remained permanent. The animal was killed
about four weeks afterwards.  Post-mortem appearances :  The tre-
phine opening filled  with cicatricial tissue.   Proximal end of sinus,
just behind trephine  opening, contains one  large granulation throm-
bus.  Cicatricial tissue filling almost the entire lumen of the sinus.
Anteriorly the  sinus is  somewhat contracted  and smooth;  no 
32
thrombus here or evidences of proliferation.   The circulation is
apparently restored by the formation of a new channel or dilatation
of a pre-existing one; this new sinus  is located to the left of the
median line.  The lateral sinuses are very much enlarged.

  Experiment No. 5.—Young yellow dog, weight about 15 pounds.
Partial  ether anaesthesia.   Longitudinal sinus exposed and trans-
versely incised  at two points in close proximity.   Hemorrhage pro-
fuse, was allowed to continue for  over half an hour in order to
estimate the length of time which would  be necessary for death to
occur  from this cause uncomplicated  by admission of air.   When
the animal appeared moribund both ends of the sinus were ligated.
The heart's action was  very feeble and irregular while respiration
was entirely suspended.  Artificial respiration was  kept up until the
heart's action ceased.  Death occurred in thirty-five minutes.  At
the examination after death no air was found in the  vessels or heart,
and death was plainly attributed in the absence of  any other cause
solely  to the loss of blood.

  Experiment No.  6.—Newfoundland  dog,  weight  50  pounds.
Partial ether narcosis.  During the  removal of bone ov.; the sinus
severe  hemorrhage was encountered from the large venous channels
in the diploe.  The  great irregularity of the external surface of the
skull led  to  a  mistake,  as the frontal sinuses were again  opened.
The longitudinal sinus was laid open  by an incision half an inch in
length  in a parallel direction to the  vessel.   Hemorrhage very pro-
fuse  for half an hour, checked at  times  by compression, when it
finally  diminished and  the wound was closed.   After the operation
the animal walked with  a staggering gait, and would run  against
objects  indiscriminately,  showing that sight was greatly impaired,
inasmuch  as the animal  had fully recovered from the effects of the
ether.   No air  was seen or heard to enter the sinus.   Heart sounds
feeble,  but otherwise normal.  Death in this case took place a week
after the operation from lepto-meningitis.   The  source of infection
undoubtedly  was again traceable to  injury of the frontal sinus, as the
earliest  evidences of  the  disease were found nearest the opening in
this structure.

  Experiment No.  7.—Old decrepit horse.   Operation  was  per-
formed  while the animal  was in the erect  position.   On removing 
33
 disk with trephine a longitudinal wound one-half inch in length was
 found in the  anterior wall of the sinus through  which bright red
 blood escaped.   Double pulsation  well marked.   Almost immedi-
 ately after the removal of the disk  of bone, and  before more than
 an ounce of blood had escaped, air entered with a loud and distinct
 lapping sound, audible  to all who  were present.   On applying the
 ear over the heart the same  loud churning sounds were heard.  As
 the head was lowered the flow of blood became more forcible and
 copious, but no  air entered ; as soon, however, as  the head was
 elevated, bleeding diminished, and  air entered during almost every
 inspiration.  Respiration became labored, and after air had entered
 four or five different times in succession the animal fell to the ground.
 In this position no further entrance  of air occurred, but the hemor-
 rhage continued copiously, the blood flowing in a  continuous stream
 with a well-marked  double  jet synchronous  with the action of the
 heart and the  respiratory movements of the chest.   The opening in
 the skull was enlarged to two inches in  length and  one and one-
 half inches in  width, so as to expose the sinus freely.  A number of
 catgut sutures  were now introduced  through both lips  of the wound,
 and on attempting to tie them  great difficulty was  experienced in
 approximating its margins,  which could be  brought  nearly but not
 completely in  contact without the  sutures tearing through.  The
 tying of all the sutures resulted in diminishing but not arresting the
 bleeding, showing conclusively that in  longitudinal wounds of the
 sinus suturing  is  an imperfect  and unreliable  measure in arresting
 hemorrhage, to say nothing  of the difficulty which is experienced in
 passing the sutures at such  great depths  and in  the  limited space
 furnished by the artificial opening in  the skull.   The  wound was
 not closed but tamponed with iodoform cotton in  order to observe
 from time to time the processes  which nature would  initiate in the
 restoration of  the  wounded sinus. Half an  hour after  the first
 entrance of air the churning sounds in the heart had much diminished,
 and almost completely disappeared after the  lapse of one  hour.
 The animal recovered completely from the immediate effects of the
air-embolism,  the respiration having again  become normal in fre-
quency and character.   After two hours  the  tampon  was removed,
but bleeding again occurred, and it  was replaced.   The animal died
twenty-four hours after the operation, probably from  the combined
effect of loss of blood,  hemorrhage into  the subdural spaces, air-
       3 
34
embolism, and senile marasmus.   At the examination of the cadaver
a subdural clot  was found  on the right  side of the brain which
weighed about half an ounce,  on the left side of the sinus a second
but smaller subdural clot was found.   Trephine opening filled by a
coagulum.   One of the sutures had lost its hold by tearing through
the tissues of one margin of the wound.  Within the sinus a small
fragile clot was found in the lateral wall of the sinus which  served
as the source of  hemorrhage into the subdural space.  This experi-
ment illustrates well the danger of plugging the opening in the skull
for the purpose of arresting hemorrhage  in case the  lateral walls  of
the sinus are injured, as it  will almost necessarily lead to subdural
hemorrhage and  expose the patient to all the disastrous consequences
incident to  this occurrence.  In this instance sponge implantation
would  not  only  have more successfully guarded against external
bleeding, but would also  have  served as a sure prophylactic against
extravasation into the subdural space.   It also teaches that suturing in
cases of wounds of the longitudinal sinus with limited defects in the
bony walls  of the cranium is impracticable, unreliable, and unsafe,
and should never be resorted to unless the dura mater is so exten-
sively exposed or separated as to permit, by making gentle traction,
perfect and complete approximation of the margins of the wound.

                  VII.  Practical Suggestions.

   In order to study the conditions which favor the aspiration of
air into a wounded sinus of the biain it is necessary to call atten-
tion to some of  the peculiarities  of  the  intracranial circulation.
Mosso,1 who has  made this  a special  subject of investigation,
asserts that the intravascular presence  in the veins within the
cranium is  higher than in the veins  of any other part of the
body.  Actual measurements have shown that the  blood-pressure
in the longitudinal sinus  is equal  to iOO-uomm. Hg.  The
probable cause of this phenomenon is that the force of distension
of the arteries within the closed and unyielding cranial cavity is
added to  the vis a tergo.   The intracranial veins show distinct
pulsations which  are  dependent upon the  pulsations  of the
arteries, and  their movements are  so plain that  they  can  be

      1 Ueber den Kreislauf des Blutes im menschlichen Gehirn, 1881. 
35
 graphically demonstrated ;  every  diastolic  movement  in  the
 artery corresponds to a venous pulse.   During the pulsations of
 the  brain, Mosso  claims  with Donders  and  Berlin, that  the
 cerebro-spinal fluid does not escape into the spinal canal.  In a
 case of spina bifida he has been able to trace respiratory but no
 circulatory movements.  When the tumor was compressed only
 a very slight increase in the volume of the brain could  be  de-
 tected at the fontanelle, even if nearly the  whole contents of the
 tumor were pressed into the spinal canal.   G. Burkhart1 has pub-
 lished the results of his  observations  on the movements of  the
 brain which  he made on four patients who had suffered  partial
 loss of the cranial vault.  The tracings  obtained  represented
 three forms of movements—pulsatile, respiratory, and vascular.
 The cerebral  pulsation has the form of a  tricrotic or  tetracrotic
 pulse, the phases following one another in about the  same time
 as those of the carotid pulse.   His observations lead him to the
 conclusion that the brain presents the same movements within
 the intact skull  as  in the  infant or when a  defect  in the skull
 exists, the result of traumatism.   The  brain expansion is syn-
 chronous with the dilatation of the vessels  and takes place in
 the direction of the vascular ramifications.   The resistance is in
 the inverse proportion to this expansion.  In the closed skull the
 excess of pressure  in the arteries aids materially the  propulsion
 of the  blood through  the veins,  and  also  that of  the sero-
 lymphatic fluid.  In the open skull the curve rises during expi-
 ration and falls during inspiration.   All actions which increase
 the respiratory movements increase the height of the curve.   A
 secondary elevation follows labored inspiratory movements,  but
 the pulse waves are never completely  effacecj.  The vascular
 curves occur  independently of respiration  or  pulsation. The
 height of the  curves bears no constant relation to their length.
They are notably influenced by psychical influences.   They are
produced  by movements of the vessels by means of the vaso-
motor nerves, and  can  be made very conspicuous by irritation
of the cervical sympathetic.   Bergmann,2  in his remarks on  the

    i London Lancet, Oct. 15, 1881.
    2 Verhandlungen d. deutschen Gesellschaft f. Chirurgia, vol. x. p. 14. 
36
movements of the brain (in opposition to Mosso) at the meeting
of the Congress of German Surgeons in 1881, insists that the
cerebro-spinal fluid acts as a regulator in maintaining the equili-
brium between the  arterial and  venous circulation  within the
cranium.   The pulsations of the sinuses of the dura mater were
discovered and studied under his supervision at Dorpat as early
as 1873.  He argues that these pulsations are very slight, and
on that account insufficient to counterbalance the arterial pulsa-
tions.   He explains  the pulsations of  the  sinuses  in  the same
way as  Donders and Jacobi have accounted for the pulsations in
the veins of the papilla of the optic nerve.   The pulsations are
the result of increased tension in the cerebro-spinal fluid  during
the arterial systole and the consecutive diminution of intracranial
pressure during the arterial diastole.   The cranium being  a
closed cavity with unyielding walls, it is not  difficult to  under-
stand that  in case  one  of the sinuses is opened by a  wound
which communicates with the  atmospheric air, the sudden loss
of blood will have a tendency to create a vacuum which is  filled
by the admission of air which reaches the  left side of the heart
with the venous blood.  All circumstances which diminish intra-
vascular and intracranial  pressure must of necessity favor the
occurrence  of aspiration  of air  into  a wounded sinus.    It  is
evident that aspiration of air into an  open wound of the longi-
tudinal or any other sinus of  the dura mater is favored  by the
following conditions:    1. The force  of  gravitation.   2. The
inspiratory movements of the chest.   3.  The condition of  arterial
circulation.  In considering the  prophylactic treatment against
the admission of  air during operations which involve  any of the
cerebral sinuses, it is of the greatest importance to keep the
head at a  level with the  heart to insure regular respiration and
to guard  against  undue  or forcible  inspiration, and, finally, to
maintain the normal  activity of the  ventricular contractions.
The direct preventive measures consist in :__
   1.  Continuous  irrigation of the field of operation.   2. Prophy-
lactic ligation of the sinus.
  In resorting to constant irrigation the fluid used should be an
aseptic  solution at  the temperature  of the  body,  which, if it 
37
 should enter the venous circulation to fill an empty space, would
 do no harm either as a toxic agent or by causing coagulation of
 the blood.  A  solution of salicylic  acid in distilled water,  or
 borated water would be  best  adapted  for  this purpose.   In
 extirpating tumors of the dura mater in the region of the longi-
 tudinal  sinus, where wounding of  this structure  becomes a
 necessity,  it  would  not only be prudent but good practice  to
 ligate the  sinus on  each side before attempting the removal of
 the tumor, as this precaution would surely and effectually prevent
 the two most dangerous and alarming accidents—hemorrhage
 and aspiration of air.  This plan was  followed  by Kuester  in
 removing  a sarcoma of the dura mater in 1881.1  Experiments
 on animals and the cadaver have convinced  me that this opera-
 tion can be performed  with comparative ease, if the defect  in
 the skull is sufficient in extent to permit the necessary manipu-
 lations, and, in the event this operation be done for the purpose
 of facilitating  the removal of tumors of the dura mater, this pre-
 caution should never be neglected.   With a tenaculum the dura
 mater is seized and  drawn forward  at the outer border of the
 longitudinal sinus, and a small  incision parallel with the border
 of the sinus should be made with a tenotome, the incision being
 only sufficiently deep to divide the dura  mater.   After making
 such an incision on each side of the sinus directly opposite each
 other, the sinus should be grasped  with  a sharp-toothed spring
 forceps and drawn forward, when a small curved sharp-pointed
 aneurism  needle is passed  into one  of the openings, and, after
 penetrating the falx cerebri underneath the vessel, is brought out
 through the  opening on the opposite side.  When  both of the
 ligatures are in place the peripheral ligature is  tied first, and
 after emptying the intervening part of the vessel  of its contents
 the proximal ligature is also tied.  If both of the ligatures have
 been properly applied the intervening portion of the sinus can be
opened or excised with the tumor without risk of hemorrhage or
the introduction of air, at the same time it will greatly facilitate
thoroughness  in the removal of diseased tissue.  I  am firmly

                1 Berl. Klin. Wochenschrift, p. 673, 1881. 
38
 convinced that the preliminary ligation of the longitudinal sinus
 will  become an  established  procedure in  all  cases where
 tumors of the dura mater are so situated that this removal impli-
 cates this  structure and that it  will render possible the removal
 of tumors which without it would  place in great and immediate
 jeopardy the life of the patient by  hemorrhage or the admission
 of air.  The process of cicatrization in the sinus is the same as
 in veins, and is accomplished in the same brief period of time.
 In accidental wounds of the sinus ligation should be resorted to
 whenever the original defect in the skull is  sufficient to permit
 the  necessary manipulations  or when simpler measures have
 failed to accomplish the same object.   Implantation of an aseptic
 sponge into a wounded sinus should  be resorted to in all cases
 of wounds  of the lateral walls of the sinus, in cases of accidental
 wounds where ligation is  impossible and where other measures
 have failed to arrest the hemorrhage.  The  sponge should be
 large enough to  make gentle pressure upon  the  inner surfaces
 of the sinus,  and  yet sufficiently  firm to arrest the circulation in
 the vessel so as to prevent the escape of blood into the  subdural
 space.  The haemostatic action of the aseptic tampon  is made
 more efficient by adding external  compression, applied in the
 form of a graduated aseptic tampon.  If the  wound  remains
 aseptic  the sponge forms  a nucleus  for the thrombus and  is
 infiltrated by connective-tissue cells from theintima and adjacent
 tissues,  and is gradually removed by absorption  as the definitive
 obliteration of the vessel  proceeds.  Small wounds of the sinus
 can be readily and safely closed with the lateral ligature applied
 in the same manner as in similar wounds of the veins.
   In recapitulation we are warranted in stating  the  following
 conclusions:—
   I. Elevation of the head is the direct and most essential cause
 in the production of  air-embolism through  a wound of the
 superior longitudinal sinus.
   2. Suturing of a wound of the superior longitudinal sinus as a
haemostatic procedure  is unreliable, and in most instances ana-
tomically impossible.
   3.  Prophylactic ligation  of the  superior longitudinal sinus 
39
 should be resorted to in all cases where this vessel is involved in
 extirpating tumors of the dura mater.
   4.  Implantation of an aseptic sponge  into  a  wounded longi-
 tudinal sinus will arrest hemorrhage without interfering with  the
 definitive obliteration of the vessel, and deserves a trial in cases
 where  the  lateral walls of the sinus have suffered injury and
 where ligation is impracticable.

 VIII.  Immediate Cause of Death after Intravenous Insufflation
                            of Air.

   Various theories have been advanced to explain the injurious
 effect of the presence of air in the circulation.  Bichat1 attributed
 death resulting  from  intravenous  injection of  air to cerebral
 ansemia produced by the presence of air in the cerebral vessels,
 asserting at the same  time that a very  small  quantity  would
 suffice to produce this effect.  As the  first argument in favor of
 this view, he claims that the heart continues to beat for some
 time  after the cessation of  animal life.   Secondly, air injected
 through one of the carotids produces death in the same way as
 when introduced into the veins.   Thirdly, the cases reported by
 Morgagni, where death was attributed to  the  presence  of  air
 which was  found  in the  cerebral vessels at the  post-mortem
 examination, and which was supposed to have developed there
 spontaneously.   Fourthly, all examinations after death revealed
 the presence  of frothy blood, mixed with  air-bubbles in both
 ventricles.  Fifthly, air injected into one of the  divisions of the
 portal vein  produces no  ill-effects until 'it reaches the general
 circulation.   Sixthly, the almost  instantaneous  death observed
 in some instances is due to the acceleration of the heart's action,
 and consequently the rapid conveyance of air into the cerebral
 vessels.   Seventhly, the  existence of convulsions  which  he
ascribes to  the irritating quality of the  air on  the brain.  He
summarizes as follows:  "We  shall conclude that in  the  acci-
dental mixture of air with the blood of the venous system, it is

          1 Physiological Researches on Life and Death, p. 186. 
40
the brain which dies the first, and that the death of the heart  is
the consequence of the death of the brain."
  Magendie, in commenting on Bichat's views concerning the
manner of death from intravenous injection of air,  remarks :
" This is not correct, and death takes place, on the  contrary, by
the cessation of the  motions of the  heart.   The  right ventricle
is filled with air, and this air, dilated by heat, so distends it that
it can no longer contract."   Magendie also claimed that small
quantities of air in veins will not result in death,  and that life  is
in  jeopardy only when the air is injected  suddenly and in con-
siderable quantity.   He relates the details of an  experiment
which  he made on a horse, where  he  injected  in rapid succes-
sion into  the veins of the animal  forty syringefuls of air, and
three syringefuls  into  the carotid artery.   The capacity of the
syringe was seventeen centilitres. The animal died three minutes
after the last injection.  At the examination of the body he found
air in the azygos vein and in the thoracic duct which contained
much lymph, as well as in the  lymphatic vessels  of the internal
surface  of the lungs.  The heart was enormously distended with
air  mixed with a small quantity of  blood.   Morgagni, Brunner,
Sprcegel, and Nysten  referred  the  cause of death  to the same
source—over-distension and  paralysis of the heart.  When death
is not produced by the mechanical effect of the air on the heart,
then the consecutive symptoms were  referred by Nysten to an
obstruction of the lungs produced by the accumulation of air in
the ultimate divisions of the pulmonary artery.   He observed
that the embarrassment in respiration often  appears as late as
twelve  hours after the introduction of the air, and becomes
greater and greater; the  bronchi  are filled with a viscid fluid,
and the animal  usually dies on  the third or fourth day.  In such
instances  no air was found  in the heart or  the vessels, but the
lungs, instead of being pink-colored, were  grayish, tinged with
brown, and loaded with frothy blood and mucus.   The same
views were entertained by  Boerhave,  Kettler, and Beck.   In
such cases  death  results from asphyxia from the  mechanical
obstruction to  the  passage of the  venous blood  through the
pulmonary  circulation.  Mery accepts the views  of Mercier 
4i
published in 1839, who attributed death  to this, that the blood
mixed with air becomes frothy, enters the pulmonary capillaries
and obstructs  them.   Physicists are aware that a capillary tube
which readily admits the passage of air or water offers a great
resistance to a mixture of air and water;  this mixture causes a
series of bubbles, separated by minute septa of liquid.  Poisenille
has shown by a series of experiments that such in fact is  the
cause of  death whenever  air mixed with  blood  has obstructed
the pulmonary capillaries.   The right heart remains over-dis-
tended and cannot be emptied.
  Blundel1 studied the effects of the intravenous injection of air
in his experiments  on transfusion of blood.   He  injected  five
drachms  of atmospheric air into the femoral vein of a small dog
in quantities of  a drachm each  at a time, without any serious
effects.   The symptoms  observed were sighing respiration,
irregular pulse, muscular tremors,  and vomiting, all  of which,
however, subsided after  a brief space of time, and the animal
recovered completely in three days.   A second experiment was
made on the same animal by blowing three drachms of pulmo-
nary air into the femoral vein without  even producing much
temporary inconvenience.  He concluded that it seemed indis-
putable that small quantities of air may be introduced  into  the
circulation without  destroying life.  Dr.  Haighton made  the
same experiments with intravenous injection of air and with like
results.   A series of experiments were made by Panum.2   The
subject of the first experiment was a small dog in which  five
cubic centimetres of air were injected into the lower portion of
the jugular vein.   No symptoms followed  immediately after
the operation.   Four  days subsequently the weight of  the
animal was reduced  from 3540 to 3030 grammes.  The tissues
around the  point  of puncture  were inflamed.   On the  fifth
day  the  animal  was  killed.   The  skin of the  animal  was
dotted with   spots of ecchymosis  resembling  the extravasa-
tions  as  they occur  in  the disease  known  as morbus macu-

  1 Medico-Chir. Trans., vol. ix. p. 65.
  2 Experimentelle Beitrage zur Lehre von der Embolic  Virchow's Archiv, vol.
v. p. 499- 
42
 losus  Werlhofii.   In the  vicinity  of  the wound,  the tissues
"were  emphysematous, emitting an  offensive odor.   Among
 other  post-mortem appearances the lungs presented several gray
 superficial stripes and spots, 1-2 lines in diameter.  In the middle
 of several of these patches were  found empty spaces which
 Panum regarded as encysted  air-bubbles.   In addition small
 isolated nodules were also found which  contained in their  inte-
 rior small bubbles of air.  These nodules contained also numer-
 ous nuclei and fat globules.   In the second experiment ten cubic
 centimetres of air were injected into the  lower portion of the
 jugular vein of a small one-year old dog.   During the first three
 days nothing was observed with the exception of rapid emacia-
 tion.  On the fourth day  the animal began to lose the hair  not
 only in the vicinity of the wound, as in the first  case, but  over
 the entire surface of the body.   Later inflammation and ulcera-
 tion attacked the point of operation.   On  the eleventh day the
 animal was killed.  The lungs  again presented subpleural  nod-
 ules, the size of a pin's head to that of a grain of sand, in which
 could  be  found large cells filled with fat molecules, granular
 cells, and fat globules in large number.   Air could not be found
 in any of them, and their relation to the capillaries of the pul-
 monary artery could not  be determined.  In the third experi-
 ment 30 cubic centimetres of air were  injected into the jugular
 vein without producing any alarming  symptoms, except rapid
 and deep respiration.  The  next day no change was observed,
 but on the following day the animal was found dead.  A careful
 examination revealed punctiform extravasations in different por-
 tions of the brain, stomach,  and liver.   The wound showed a
 healthy appearance.   The  lungs contained many  very small
 yellowish-white nodules and points of extravasation one to two
 lines in diameter.   The hemorrhagic infarcts  contained each a
 minute cavity filled with  air.   The nodules also  contained air.
 From  these experiments  it appears that the  air-emboli which
 passed through the pulmonary capillaries produced local dis-
 turbances in the minute vessels in the skin and gastro-intestinal
 canal,  while the  air-emboli in the ultimate  branches of the pul-
 monary artery gave rise to circumscribed foci of inflammation. 
43
   Picard1 found after insufflation of air into the portal vein in-
 tense hyperemia in the distal portion and radicles of the vessel,
 the same as after ligation.   At the commencement of the insuf-
 flation the blood pressure in the femoral  artery and one of the
 rectal veins was about the  same, but after a while the pressure
 in both was simultaneously  diminished, but the positive pressure
 lasted longer in the vein than in the artery.  The action of the
 heart was  increased,  the respirations  became slower, and the
 temperature in  the  rectum was gradually  reduced.   As  an
 interesting physiological fact it is mentioned that after insuffla-
 tion of air into the portal  vein no sugar could be found in the
 liver, and  the fibrin in the portal blood was diminished.
   The  experiments of  Magendie, Bouillaud, and later those of
 Couty,2 prove conclusively that  in cases of entrance of air into a
 peripheral  vein  the air collects almost exclusively in the right
 side of the heart; only a minute quantity entering the left side
 through the pulmonary capillaries.   Referring  to this question
 Flint says :  ," The production of death from air in the veins is
 purely mechanical.  The air, finding its way to the right ventricle,
 is mixed  with  the blood in the  form of minute bubbles and
 passed  into the pulmonary artery.   Once in this  vessel, it is
 impossible for  it  to pass  through  the capillaries of the lungs,
 and  death  by suffocation is the inevitable result if  the quantity
 of air be  large.  It is because  no  blood  can pass through  the
 lungs that the left cavities of the heart are  usually found empty."3
 If the quantity of air introduced is small, or the entrance repeated
 in small quantities, the air collects in  the capillaries of the pul-
 monary artery as air-emboli, obstructing  the circulation in the
 impacted vessels, but  a sufficient number  of vessels remain per-
vious to  maintain the  circulation, and  life is prolonged until the
equilibrium of the circulation  is restored by the absorption of
the adventitious air.   No traces of air are found in the arteries,
only a small quantity passing into the vense cavse through  the
tricuspid  valve, which has  been rendered insufficient  by  the

  i Sur les injections d'air dans la veine porte.  Gaz. Mel. de Paris, No. 6, 1873.
  2 Etude experimenlale sur l'entifie de l'air clans les  veines,  Paris, 1S75.
  3 Physiology of Man, Blood, Circulation, Respiration, p. 323, 1866. 
44
presence of air.  When a considerable amount of air has entered
the right ventricle of the heart mixed with the blood, the air is
separated from it, and, its specific gravity being  less, it rises to
the highest point of the chamber in  contact with  the anterior
walls;  besides it expands and by this over-distension it impairs
the muscular contractility which even in a normal  condition is
insufficient to empty the cavity completely.   The impediment
to the circulation being the presence of the large air-embolus in
the right ventricle, which on account  of the higher temperature
increases in volume,  sudden death will take place in the diastole
by an arrest of the heart's action from paralysis by over-disten-
sion.   If the animal  escapes instantaneous  death  from this
cause, the heart is inadequate to force the blood from the right
ventricle through the pulmonary circulation, as its  efforts  are
expended in compressing  the air; only a minute  quantity of
blood being forced into the lungs.   In proportion as the amount
of air and blood in the right ventricle increases, the right  side of
the heart is expanded and the volume of blood in the lungs and
the left heart is diminished.  At last  the distended walls  of  the
heart prevent perfect closure of the tricuspid  valve, giving rise
to venous  pulsation, a  constant  symptom in  all cases  of air-
embolism which  prove  rapidly fatal.  On the advent of this
complication the intra-arterial pressure  in  the pulmonary and
peripheral  arteries diminishes, which  further  enfeebles the pul-
monary circulation, at the same time  it produces acute ansemia
of the brain, and  death results from ansemia of the brain or
asphyxia.  Such  is the mechanism of death in cases of entrance
of air  into the venous  circulation,  and  at  the same time it
offers  an explanation  why  in  these cases  the  air  is   found
mostly  in  the  right side of the  heart  and the  large venous
trunks.  These facts also corroborate the observations of experi-
menters that certain animals succumb more readily to the pres-
ence of air in veins than others.  The tolerance of intravenous
air is most marked  in  animals with well-developed  respiratory
organs  and  a proportionately powerful  right  ventricle.  In
horses, for example, the volume of the  right  cavities is smaller
and the muscular structure more powerful, circumstances which 
45
 explain the fact that entrance of air into the veins of these ani-
 mals does  not easily kill  them.  The circulatory apparatus of
 the dog offers the  least resistance to intravenous air.    Rey
 blew air into  the jugular veins of  horses  after venesection
 without producing death.  Small amounts of air produced no
 result whatever, and a volume of air equivalent to two  expira-
 tions proved fatal only in debilitated animals.  Some animals
 remained well  after  leaving a  canula in  the jugular vein for
 several hours.  Death was sure to follow if after the insufflation
 of air the vein was ligated.   Animals  who  have previously lost
 large quantities of blood readily succumb to intravenous admis-
 sion of air.
   Laborde  and Muron, who studied the effects of intravenous
 and intra-arterial insufflation of air, placed great  stress on the
 manner in  which  the injections are made in determining the
 gravity of the symptoms.  They observed  that in case  the in-
 sufflations into  veins are made slowly and repeated at intervals
 large quantities were tolerated without exciting serious symp-
 toms.  If, on the other hand,  they were  made suddenly and
 with  force, and the quantity  of air  was  considerable, death
 resulted almost instantaneously from arrest  of the  heart's action
 in the  diastole, an occurrence which  was  attributed  by these
 authors to over-distension of the right  side of the heart.
   In  repetition, it may be  stated, that the  immediate cause  of
 death after intravenous  injection of air has  been referred by
 different experimenters to :—
   r.  Mechanical  over-distension of the right ventricle of the
        heart and paralysis of this organ during the diastole.
   2.  Acute cerebral  ischaemia.
   3.  Asphyxia from obstruction to the pulmonary circulation
        consequent upon embolism of  the pulmonary artery.

             IX. Intra-Arterial Insufflation of Air.

  As the accidental admission of air never takes place in wounds
of the arteries  on  account of the high degree of intravascular
pressure and the absence of any aspiratory force it is not  sur- 
46
 prising that the effect of the artificial introduction of air into
 these vessels has been made less frequently an object of experi-
 mental research than intravenous insufflation of air.  The subject
 is devoid  of any practical value,  and the interest attached to
 it is  of a  purely  scientific nature.   As we  have already seen,
 Bichat entertained the idea that atmospheric air acts as a  direct
 irritant to the  substance of the brain when  brought  in contact
 with  that organ through the medium of the cerebral vessels, and
 death from insufflation of air, whether into veins or  arteries, was
 invariably  attributed by  him to cerebral  anaemia.   Panum,1 in
 his researches on embolism, made arterial insufflation of air also
 a  subject of experimentation.   A  rapidly fatal  termination fol-
 lowed the  injection  of 4 c. centimetres  of  air  into the  lower
 portion of the carotid  artery  of  a medium-sized  dog.   The
 rnfundation  was  superseded  immediately by  severe  general
 convulsions, alternated by violent attacks of rage.   The animal
 foamed at  the mouth, and had  involuntary discharges from the
 bladder and bowels, the eyes became prominent, and the pupils,
 at first dilated,  contracted, and remained so permanently.   The
 animal  soon became quiet and motionless.   Respiration and
 heart's  action  slow.  The right  anterior and  both posterior
 extremities were extended and rigid, while  the left  front leg
 remained  relaxed.   Conjunctiva insensible, while touching the
 cornea produced contractions  of the eyelids.  For two hours
 the animal  remained in a  condition resembling anaesthesia  with-
 out changing its position, with slow pulse and respiration,  when
 life ceased  without a tremor or convulsion.   The post-mortem
 examination showed numerous punctiform ecchymoses in the
 gastro-intestinal mucous membrane,  the liver, diaphragm, and
 abdominal  muscles.  The superficial  vessels of the  brain,  more
 particularly the veins, were extremely hyperaemic;  the jugular
 veins  were  distended to their utmost with blood.  The small
arteries contained many air-bubbles, so that the smallest vessels
presented varicose dilatations which resembled a string of pearls.
The large vessels at the base of the brain also  contained air, and
1 Op. cit. 
47
 numerous  red spots were  disseminated  throughout the  white
 substance of the brain.
   Laborde and Muron1 witnessed after the introduction of 20-60
 c. cm. of air into the carotid artery of dogs,  when injected in a
 peripheral direction,  that death  was produced rapidly and was
 always preceded by tetanic  convulsions and labored respiration,
 while if the quantity of air injected  was smaller, and especially if
 the air was  thrown in in divided doses, the animal often survived
 the experiment for twenty-four  hours.   In the latter  class  of
 cases the operation was followed by tetanus, vomiting, paralysis,
 and coma.   The autopsy revealed softening of the  brain, and
 capillary hemorrhages, especially  in the middle  portion of the
 brain,  the medulla  oblongata, and  in  the posterior lobes of the
 cerebrum.   The  intra-arterial insufflations of air in  all  these
 experiments were immediately followed by grave cerebral symp-
 toms which can only be interpreted by the constant post-mortem
 appearances, air-embolism of the cerebral  vessels, and extreme
 ischaemia of the  brain.  The presence of air  in the arteries,  on
 the left side of the heart,  is followed by  an entirely different
 series of phenomena than in the veins on  the right side of the
 heart.  The acute ischaemia of the  brain  thus induced is invari-
 ably manifested by tetanic rigidity  of the  voluntary muscles and
 almost complete suspension of the  respiratory movements of the
 chest.  The contractions of the left ventricle are  so powerful as
 to overcome these additional impediments and to completely
 evacuate the chamber.   The air is expelled as soon as it enters
 and  is distributed  throughout the whole arterial system.  It
 must be readily conceived that the air when it has reached the
 aorta will rise into the carotid arteries and thence into the cerebral
 vessels,  distending  them to their  utmost capacity.   In  such
 instances death results  from sudden cerebral anaemia before the
air can gain entrance into the venous  system through the  capil-
laries.  That the presence of air  is detrimental to the nervous
system  has  been  established  by experiments  on  animals.
 Bohnius  attributed  to the air when introduced into the vascular

         1 Virchow u. Hirsch's Jahresbericht, vol i. p. 268,  1873. 
48
system poisonous properties, and this opinion is entertained by
Neudorfer even at the present time.   Copeland believed that
the oxygen of the adventitious  air combines with the carbonic
oxide in the venous blood producing carbonic acid.  These and
similar theories  do not explain the phenomena observed after
insufflation of air.  The symptoms during life, and post-mortem
appearances point directly towards physical  obstruction in the
bloodvessels by air-emboli which suspends  the  function of one
of the vital organs, and consequently must  be  regarded as the
immediate or direct cause of death.  Insufflation of air into the
carotid artery  towards  the brain  is almost immediately  fatal.
If a  moderate quantity of air  is forced through the  arterial
system into any other organ except the brain, except by forming
a temporary obstruction in the circulation, it does no particular
harm and is in a short time removed by absorption.   This fact
may have induced Flint to make the following remarks concern-
ing this subject i1   " Air injected into the arteries  produces no
such  serious effects  as air in the veins.   It is arrested in the
capillaries of certain parts, and in the course of time is absorbed
without having produced any  injury."
  The danger arising from the introduction of  air  into the
arteries or  left side of the heart arises  from obstruction to the
circulation  through the cerebral vessels by air  emboli and the
cessation  of the functions of the brain consequent upon an almost
complete  ischaemia of this organ.  The mechanical distension of
the left side of the heart by the accumulated air  is overbalanced
by the powerful contractions of the left ventricle,  which are  suffi-
cient to empty the chamber almost completely, and to force the  '
air into the ultimate distributions of the arteries causing acute
anaemia  in distant organs,  but  more particularly in  the brain.
In these  instances  the air is  forced  directly  into the  cerebral
vessels either by the injecting force or the powerful  contractions
of the  left ventricle, and if death takes place it follows as the
direct result of acute cerebral ischaemia.
1 Op. cit., p. 324. 
49
             X.  Clinical Study of Air-Embolism.

  All  physiologists agree that regular and  deep inspirations
produce a powerful aspiration  in the large veins near the base
of the heart, more particularly in the jugular and subclavian
veins.  This fact  is so well known that the base of the neck and
the clavicular regions are frequently referred to as the "danger
zone."  During the inspiratory act the chest expands, and the
flow of venous blood  is  accelerated  towards the cardiac or
proximal side.  A diversity of opinion still exists among authors
in regard to the distance to which this  force directly affects the
venous circulation.  Experiment and clinical observation  have
shown that the danger of entrance of air into wounded veins is
increased  as the  wound approaches  the heart.  Berard studied
the anatomical conditions of the vessels where entrance  of air
has most frequently taken place, and he came to the conclusion
that this accident can only happen in the event when the wounded
vessel  is empty, and its  walls are prevented from collapsing, and
the wound remains patulous.  He found these conditions nor-
mally present in the sinuses of the dura mater, the hepatic veins,
the superior vena  cava,  the  internal jugular, the subclavian, and
axillary veins, because  the walls of all  these vessels are firmly
fixed  to the adjacent tissues, which prevents  their collapse on
being wounded.   It has been further shown that  the admission
of air  is favored  by pathological conditions  which  affect the
veins in a similar manner, as the existence of induration of their
walls, the result of chronic inflammation, or  infiltration by neo-
plasms.  Experience has corroborated these views, inasmuch as
it has been shown  that this accident has occurred most frequently
in operations in the vicinity of veins which, from their anatomical
location, are prevented  from collapsing by firm and unyielding
layers  of fascia, and vessels which are, or have become, adherent
to unyielding  tissues.   Again,  it is always very justly feared in
removing tumors which have  become  adherent to large veins,
as the morbid  process  frequently has impaired the normal resi-
liency  of the vessel so as to keep its lumen patent in the event
it is wounded during the dissection.
       4 
                             50
  In  33 cases of intravenous  aspiration of air collected  by
Couty,1 air entered the external jugular 9 times, the axillary 8
times, the internal jugular 5 times, the subscapularis 3  times,
the facial twice, the  anterior jugular twice, the  occipital  twice,
and twice one of the anterior thoracic veins in close proximity
to the clavicle.   In  1864 Greene collected 67 cases where  air
had entered a vein during  an operation.   The greater number
of cases occurred during extirpation of tumors in the region of
the neck, chest, and  axilla.   Twice the accident  took place in
disarticulating the humerus at the shoulder-joint (Cooper, Del-
pech); once on extirpating  the scapula and clavicle (Mussey);
twice  on tying the  subclavian artery (Rigaud, Clemot);  three
times on bleeding from the external jugular vein, three times
on  bleeding from the median vein, and once on passing a  seton-
needle through the tissues in the regions of the neck.  Among
the wounded veins the external jugular is mentioned 13  times,
the internal jugular  10 times, the subclavian  and axillary each
once.   In the remaining cases the vein is not specified, or the
injury  involved a branch  in close  proximity to the specified
vessels.2  All causes  which interfere with the  free  return of
venous blood prevent  the admission of air; while, on the other
hand, all influences which promote the venous circulation, such
as  an unimpaired vis a tergo, regular deep inspiration, and the
force  of gravitation predispose to  this accident.   Soon after
Beauchene made known his case the Royal Academy of  Medi-
cine of Paris appointed a commission to investigate the subject.
In  the  report it  is stated  that the results of the experiments,
which were made principally on dogs, had proven that the con-
ditions  necessary to determine the entrance of air consisted in
making the wound in  the vein anywhere within  the area  of the
venous pulse, or, at  any rate, only a short distance from  it.  If
the wound was located  at a greater distance and beyond the
influence of the venous pulsations,  no air would enter, although
the wound  was kept  open.  The experiments were also to deter-
mine the extent of the  venous pulse, and the conclusions arrived

         1 Op. cit.
         2 American Journal of the Medical Sciences, 1864, p. 38. 
5i
 at were that the brachial and axillary veins were  beyond  the
 venous wave, while the subclavian and lower third of the jugular
 veins were the seat of pulsations, consequently wounds of  the
 veins in the localities  were liable  to admit air.   The sound
 produced  by the entrance of air  is described as  resembling  the
 lapping of a dog or cat, and that it always occurred during, and
 synchronous with, inspiration; but sometimes, when it was heard
 more frequently, it accompanied  the diastole of the right ven-
 tricle.  After the air had entered the vein, the sound which
 could be heard on auscultation over the heart was  described as
 a "bruit de soufflet,"  synchronous with the  action of the heart.
 In regard  to the effect of the aspirated air it was decided that, in
 order to produce a  fatal result,  it was not  only necessary that
 the amount of air introduced should be considerable, but that it
 must be thrown into the vein with some degree of force.
   Hertwig called special  attention to the fact that aspiration of
 air is not as frequent an  accident as is generally supposed, and
 that  for its occurrence it is necessary that the peripheral flow of
 blood to the wound must be obstructed, that the edges of the
 vein  wound must be drawn apart, and  finally, that even  the
 introduction of a canula  into  the vein is necessary to admit a
 sufficient amount of air to produce serious results.
   The first case of admission of  air into a vein that was recog-
 nized and verified by a post-mortem  examination  occurred  in
 the practice of Beauchene,  and is described by F. Magendie.1
 As the case is of great historical and  scientific  interest, I  will
 relate it as described by Magendie.

   A locksmith, 23 years of age, had for five years a large tumor on
 the right shoulder and clavicle.   His acute sufferings induced  him
 to enter the hospital to have  it removed.  It was  necessary in the
 operation to remove  the  middle  portion of the clavicle.  Thus far
 the success was complete;  but little blood was lost, the pulse was
 good,  and  the breathing easy, when the patient  suddenly cried
 out:  "My blood is leaving my body! I am dead!"   At  the same

  1 Physiological Researches on Life and  Death, by X. Bichat, with Notes by F.
Magendie.  Translated.  Boston, 1827, p.  188. 
52
moment he  became stiff, lost  his consciousness, and was  covered
with a cold sweat.  A singular and rather loud noise was heard  in
the interior of his chest.  The surgeon thought that he had opened
the pleura by removing a portion of the clavicula, and thus given
access  to the air and to the  blood to the right side of the thorax.
The fingers of an assistant were immediately thrust into the bottom
of the  wound with a view of stopping the supposed opening  in the
pleura, and the surgeon endeavored to introduce into the thorax the
extremity of a sound of gum-elastic.  When he thought that he had
succeeded he drew with his mouth the air which he supposed to be
effused in  the pleura.   He wished then to proceed to the dressing,
and, in order to do this, he substituted for the fingers of the pupil,
which  were at the bottom of the wound, a sponge  covered with
wax;  but  the moment the sponge took the place of the fingers, the
same noise  that was at first  heard, and which  had  ceased  in  an
instant, was renewed with more force than  before.   The  syncope
and cold sweat still continued.  Water  thrown into the face made
him give some signs of life, but  he died a quarter of  an hour after
the appearance of the accident I have first described,  and forty-five
minutes after the commencement of the  operation.  The body was
examined  the next morning.   They expected to find the right pleura
open, much blood and air effused  into its cavity, and  the lungs on
that side collapsed.  Nothing of the kind was found.   The pleura
was whole and there was no effusion in it. The lungs were as usual,
but an opening of half an  inch in extent  was  discovered in the
external jugular vein, at the place where this vein opens  into the
subclavian.  The cavities of  the  heart were large, but contained no
blood.  Bubbles of air were  observed in the vessels  of the brain;
the other vessels were not examined.

   In order to study some of the conditions under which air has
been aspirated into veins, and for the purpose of ascertaining the
effects of such accidents in  man, I will introduce  a number of
well-authenticated cases which will represent a great diversity in
the point of entrance, and  will also aid in the establishment of
the fact that this accident  can occur outside of the regions of
venous pulse, and always occurs during inspiration, and is never
produced by the aspiratory function of the heart. 
53
   External Jugular.   Barlow's case.1  The patient was  a female
suffering from a tumor seated on the side of the neck, which  had
been increasing in size for several years ;  its  base  was extensive,
and occupied the whole of the lateral  and posterior parts, extend-
ing from the ear to near the sternum, and side wise from the thyroid
gland to the sterno-mastoid muscle, under which a part of the tumor
was situated.  The patient was seated in a reclined chair, supported
by assistants.  Two superficial elliptical  incisions, ten inches in
length,  were made downwards from a little  below the ear, "when
on proceeding to dissect the skin aside to get at the basis  of the
tumor, a sudden and unexpected hissing and gurgling  noise rushed
obviously from a large divided empty  vein, and the patient expired
instantly, without either sigh, groan, or struggle, and every effort to
restore  animation became fruitless."   The  divided vein  appeared
larger than the normal external jugular, but the reporter  believes
that it was this vessel or an anomalous vessel greatly enlarged.  As
the incisions must have traversed the external jugular,  according to
his own description, it was undoubtedly this vessel  which was in-
jured.  It is distinctly stated that the vessel was flabby and  empty,
and that the  instant the atmospheric air gained  access and filled the
vacuum, the hissing noise  ceased,  the  patient  expired, and  the
mouth of the vessel collapsed.

   Remarks.—In  this case the admission of air was favored by
the  dilatation  of the  vein,  and the  semi-erect position  of  the
patient.   The latter  factor  produced the emptiness of  the vein.
The  instantaneous death without any  symptoms preceding  it
can only be  explained by the fact that the air entered with force
and in large quantity  the right ventricle and  arrested the heart's
action by over-distension.

   Internal Jugular.  Ulrich's case.2   The operation was performed
for the removal of a tumor involving the left side of the neck.  It
was found  that the tumor was attached to the deep vessels  of the
neck, and in severing its connection, the internal jugular vein  was
opened.   No hemorrhage  followed, the vessel  remained open  like
an  artery,  and air entered immediately.    The patient  fainted;

            1 Medico Chirurg. Trans , vol. xvi. p. 29.
            * Rust's Chirurgie, Berlin, 1836, vol. xvii. p. 565. 
54
twitching of the muscles of the face, opisthotonos, a few slow respi-
rations followed, and the patient was dead.   The vein was  found
obliterated  above the incision, and thickened, and  more resistant
than normal where the wound was inflicted.  The reporter attribu-
ted the ingress of air to aspiration of the heart, and death to paraly-
sis of this organ.

  Remarks.—The  pathological  changes in the vein above the
wound, interrupting entirely the column of blood from above as
well as the thickening of the incised vein walls were potent fac-
tors which  determined  the entrance of air.  As this operation
was performed before anaesthetics were  used, we may be almost
certain that the patient was in a sitting or half-reclining position
during the operation,  thus  favoring greatly venous return  and
ingress of air.   The entrance of air in this instance is brought
in connection with the suction power of the heart  by the author
in accordance with the prevalent  doctrine  of the French  Com-
mission.

  Internal Jugular.  Dupuytren's  case.1   The operation  consisted
in the removal of a tumor of a fibro-cellular character of considera-
ble size from  the neck of a female,  22 years of age.  No serious
obstacles presented  themselves until  the last deep attachment was
severed with  the. knife when suddenly a  prolonged hissing noise
(Soufflementprolongs) was heard resemblingthe sound produced  by the
entrance of air into a vessel from which it had been exhausted.    The
patient immediately proclaimed "I am dying," and instantaneously
dropped down on the  floor, a lifeless corpse.   As no other cause
was found which could in any  way account for the sudden  death,
the fatal issue was attributed  to the entrance of air into the internal
jugular vein.   The  following account of  the post-mortem appear-
ances fully warrant this supposition : "The  right auricle was dis-
tended with air like a bladder, which rushed out when cut open with-
out any admixture of blood.  Fluid blood was found  in the different
vessels.  Great  quantities of  air  were  found in all the vessels.
There  was no other unnatural  appearance in any other part  of the
body."
1 Medico-Chir. Trans., vol. xvi. p. 301. 
55
    Remarks.—The editor of the Medical and Chirurgical Review
 explained the entrance of air in this case as follows : " It proves
 that the heart acts as a sucking  as well as forcing pump, other-
 wise  air could  never have passed from a cut vein in the neck
 down into the right chambers of the heart.  It is highly proba-
 ble that, in consequence of the morbid state of the parts, the
 mouth of the cut vein had  remained patulous, and  thus  readily
 admitted the air."  As no mention is made of the occurrence
 of hemorrhage, the vein was probably empty, a condition which
 might have been owing to the position of the patient during the
 operation or the pressure of the tumor.   It is also reasonable to
 assume that, on account of the intimate connection of the tumor
 with the vessel, the  former  so altered the structure of the latter
 as to  prevent closure of the wound, all of these causes combined
 resulting in aspiration of air during inspiration.

   Facial Vein.   Mott's case.1  The operation consisted in extirpa-
 tion of the parotid gland, the seat of a scirrhous tumor.   The facial
 vein was opened, where  it passes over the base of the lower jaw, in
 dissecting the integuments from the tumor in the early stage of the
 operation before a single artery was tied.  At the instant this vessel
 was opened, the attention of all present was arrested by the gurgling
 noise of air passing into some small opening.   The breathing of the
 patient at once became difficult and laborious, the heart's action
 violent and irregular,  his features were distorted, and convulsions of
 the whole body soon  followed to  so great  an extent as to make it
 impossible to keep him on the table.   He lay upon the floor in this
 condition for nearly half an hour, as all supposed in articulo mortis.
 The convulsions  ceased  gradually, his mouth  was distorted, and
 complete hemiplegia was found to have taken  place; after an hour
 had passed he could speak, but the use of his arm and leg was only
 recovered completely  after the lapse of a day.

   Remarks.—Although not  stated, it was undoubtedly true that
in this instance  the  facial vein was enlarged, and its walls had
lost their normal resiliency, thus favoring  the  ingress of  air.
This case is also of  interest, as from the predominance of the
' Ibidem, p. 32. 
56
cerebral symptoms it is apparent that some of the air must have
passed through  the  pulmonary circulation  and  have gained
access into the cerebral vessels  from the  left ventricle, giving
rise to symptoms of cerebral embolism which disappeared as the
air was absorbed.

  Axillary Vein.    Bransby Cooper's  case.1   The  patient  was a
female, 19 years of age, who was the subject, of a malignant  tumor
of the right  humerus which required amputation at the shoulder-
joint.  The operation was done by making a double  flap, the sub-
clavian artery in the mean time being compressed against the first rib.
There was no loss of blood.  The subclavian  artery was secured,
compression  being  kept up, as there were small vessels which re-
quired ligation.    As the operator was  removing an enlarged  gland
from the  axilla, he  heard  distinctly a peculiar  gurgling noise,  like
air escaping with  fluid  from a narrow-necked bottle.  At the same
moment  the  patient fell into a state of collapse which threatened
immediate death.    The face was deadly pale, the pupils fixed and
insensible to light, the pulse small and fluttering, at intervals regular,
respiration hurried  and feeble, and at irregular  intervals attended
with a sigh.   The patient  was placed in the recumbent position, the
flaps  closed,  and  stimulants applied; but an hour elapsed before
she had  sufficiently recovered  to  be removed  from  the operating
room. Subsequently, when placed in bed,  she  maintained a con-
stant motion of alternate flexion and extension of the right leg which
continued for several days, at the same time she complained of pain,
extending up the  right side of the neck and head.   The next day
the pulse varied  from 140-150  per minute, which  remained  the
same for two days.  She gradually rallied and recovered completely.

   Remarks.—In  this  case the axillary vein was divided at a
point where  its walls are  firmly fixed and its lumen kept patent
by dense connective tissue which surrounds  the vessel, a condi-
tion which   predisposes  to aspiration  of  air.  Pulmonary  air-
emboli obstructed  the passage  of blood through the lungs, a
circumstance which would serve to explain the rapid respiration
and  the  accelerated  action of the  heart until the obstructing
cause was removed.
1 Med.-Chir. Trans., vol. xxvii. p. 41. 
57
   Axillary Vein.  Courvoisier'scase.1 The operation was performed
 for the removal of a recurring cancer of the breast, and  included
 the extirpation of infiltrated and ulcerated axillary glands.   As the
 dissection reached the upper margin of the mass of axillary glands
 a  lapping (schluerfendes) sound was suddenly heard ;  at the same
 time the patient, a robust woman 58 years of age, sank into a con-
 dition of collapse.   The central portion of the  vein  was  at  once
 closed  by digital  compression,  and artificial respiration  with the
 administration of stimulants were successful  in restoring her  after
 the lapse of half an hour.  Both ends of the vein were ligated, and
 the central  ligature  included the forceps, which were allowed  to
 remain.   The patient recovered.

   Remarks.—In this  instance  the entrance of  air was again
 determined  by the anatomical  location of the  vein wound, to
 which may have been added cancerous infiltration of the para-
 vascular tissues, which rendered  the vein  walls  still more un-
 yielding.   The amount of air  admitted must have  been small,
 to judge from the  evanescent  nature of the symptoms which
 followed.

   Anterior  Thoracic  Vein.   Amussat's  case.2  The patient was  a
 woman, 47 years of age, suffering from a scirrhous  affection of the
 right  mammary gland and the subjacent and surrounding tissues.
 The breast and adjacent tissues had  been removed, and  the operator
 was dissecting towards the opposite side, when suddenly, on making
 an incision into some suspicious  granulations on the inner  side of,
 and below the left clavicle, he and  three other surgeons who were
 assisting him heard a sudden, distinct,  interrupted sound, as of air
 passing into a cavity through a narrow opening.  The patient ex-
 claimed, "I am dying," and appeared to be suffocating.  A repeti-
 tion of the same sound convinced the operator that air  had  entered
 through a wounded vein, and he placed his finger on the spot from
 which the sound proceeded.  The patient's condition became criti-
cal ; a cold sweat covered her face, her eyes  were turned upwards,
and all around her thought her dying.   The orifice of the wounded
vein could be distinctly seen.   The chest was compressed with  a

         1 Correspondenzblatt fuer Schweizer Aerzte, p. 205, 1880.
         2 Gazette des Hopitaux, July 6, 1837. 
58
 view to  force out the air from  the vein, the wounded spot being
 compressed during the expansion of the chest.   The  patient soon
 began to show signs of improvement, when the operation  was com-
 pleted, and the  vein  with a portion of the tissue was tied.  The
 patient recovered completely.

   Remarks.—Although  the  particular  vein  wounded in this
 instance is not specified, it was  undoubtedly a branch of the sub-
 clavian vein, the wound being  in  close proximity to the latter
 vessel.  This case furnishes a good  illustration of the  fact, that
 veins of comparatively small calibre, when wounded near  their
 proximal termination into a large vessel, may serve  as  points of
 entrance of air under the same circumstances as when  the prin-
 cipal trunk is injured.

   Superficial Cervical Vein.  Trelat's case.1  M.  Trelat related, at
 a  meeting of the Societe de Chirurgie of  Paris, an  important case
 in which  sudden death occurred in a patient from whom  he was
 proceeding to remove a submaxillary tumor.  The  patient turned
 ghastly pale, and the heart's  action  ceased suddenly.  Artificial
 respiration and electrization of  the phrenic nerve  induced some
 respirations and  a slight return  of color after fifteen  minutes, but
 ineffectually.   At the  post-mortem examination a  small vein open-
 ing  into  the  external  jugular  was  found  to have  been  partially
 divided;  in the jugular was  a  long  clot interspersed with air-bub-
 bles, and other bubbles of air were found in  one of the mediastinal
 veins and the posterior cardiac vein, and a very notable quantity of
 air in the right chambers of the heart.

   Remarks.—Several members  of the society argued that death
 in this instance  was due to the  anaesthetic, and  not to the
 entrance of air into the vein.    Roux and Giraldes claimed  that
 in several cases of  death from chloroform they had found gases
 in the heart, in  the  vena cava, and  even in the veins  of the
pelvis, but M. Depaul, in reply, properly  and  forcibly pointed
 out  that the air in this case  occupied only the veins going  to
the heart and the wounded vein.
1 British Medical Journal, March 16, 1872. 
59
   Femoral Vein.  The only well-authenticated case of aspiration of
 air into the femoral vein that  I  have been able to find  is recorded
 in the Medical and Surgical History of the British Army in Turkey
 and the Crimea, vol. ii. p. 277, and refers to the sudden death from
 this cause of a soldier who had  suffered amputation of the thigh.
 Three days and one-half after the operation he died suddenly with-
 out any obvious cause.  At the necropsy, twelve hours after death,
 it was ascertained that the right cavities of the heart were distended
 with a mixture of blood and air, and the same condition was found
 in the two iliac veins and the inferior vena cava.

   Remarks.—As  the time which  had intervened between the
 operation and the fatal accident was more three days, it is neces-
 sary to  assume that the venous thrombus had been removed by
 suppuration, thus opening the vein for the  admission of air, or
 that the supposed air found  in the heart and vessels was not air
 but gas which had developed  in the wounded  parts, and had
 gained  entrance into the venous circulation.  This latter suppo-
 sition is strengthened by the statement that the surfaces of the
 flaps were  separated  by gaseous products, and that the femoral
 vein was not closed but lay open on the surface of the stump.

   Internal  Saphenous Vein.  Warren's case.1  The operation was
 done for the removal of a tumor from the inner surface  of the
 thigh.   In the dissection the internal  saphenous vein was wounded;
 the event was promptly announced by an audible and distinct suck-
 ing sound  produced  by the entering air.  No alarming symptoms
 followed, as the further  ingress of air was promptly prevented by
 closure of the vein.

   Uterine Veins.  That the entrance of air into the uterine veins
might be a cause of  danger after parturition was suggested by
Legallois in 1829.  Dr. John Rose Cormack read a paper on
this subject  before the Westminster Medical Society in  1850
when he gave the details of three cases that had occurred in his
neighborhood.   Many authorities doubt the possibility of admis-
' Gazette Medicale, No. 52. 
6o
sion of air  into the uterine veins after labor.   Julius M. Kolb1
alludes  to  this subject as follows:   " I have  not seen  a case
which convinced me that air  had passed  into the open veins of
a recently delivered uterus, and I cannot conceive the mechanical
possibility  of such an  occurrence."   Bessems,  Lionet,  Lever,
Wintrich, Berry, and  Simpson assert that  they have met with
such instances, and a  sufficient number of well-authenticated
cases have  been placed on record which  leave no further doubt
as to the possibility of sudden death in puerperal women  from
entrance of air into the uterine sinuses.   In a recent number of
the  Wiener  Medicinische  Zeitschrift, Braun gives  three  fatal
cases from  the introduction of air into the uterine veins ;  in two
of three the uterine douche was used, in one to produce abortion,
in the other after  delivery of twins, and  the patients died in a
short time, one indeed within twenty  minutes.   Post-mortem
examination showed  air in the uterine veins, in the ascending
vena cava,  and in the veins of the  heart.   The third  case was
that of a woman who  had been delivered  lying upon her left
side, and was then  turned  upon her  back; massage was  made
over the uterus, she gasped and died in a few minutes.  Braun
suggests that in the change of position a volume of  air entered
the uterus, and the manipulation, instead of driving  it out, forced
it into the uterine veins.  Bischoff refers to two cases that came
under  his  observation.2   Dr.  Draper3  has reported two cases
where instant death occurred from efforts  to cause criminal abor-
tion.  The  post-mortem examination proved in each case the
presence of air in the veins.
   Mr. George May4 reports three cases which  occurred in his
vicinity. The patients  died respectively immediately, six hours,
and eight  days after delivery, and  in all  of them  post-mortem
examinations showed the  presence of air in large quantities in
the inferior  vena cava and the right side of the heart.   An inte-

  ' The Pathological Anatomy of the Female Sexual Organs, 1868, American
Translation.
  2 Corresp. bl. f. Schweizer Arzte, p. 206, 1880.
  3 Boston Med. and Surg. Journal, January, 1883.
  1 British Med. Journal, June 6, 1857. 
6i
resting  account of this  accident is given by Dr. George Cord-
went, and relates to a case that came under his observation.1

  His patient was  28 years  of age.   During the delivery, at full
term, her  expulsive pains became urgent, and at her request she
was permitted, in the absence  of her medical attendant, to remain
standing;  after a few severe pains the child was expelled, and after
falling on the floor dragged with it  the whole placenta.   Almost
immediately afterward a kind  of gurgling sound was heard by the
attendants, but whether it arose from rumbling in the bowels they
could not say.  The patient remained about one minute standing as
before and holding  onto the bed-post;  she then cried out:  "I
can't  see! I  feel faint!  lay me on the bed," and  expired almost
instantly.  At the necropsy, 24 hours after death, it was shown that
the uterus externally presented the normal appearances of a recently
delivered  organ, except that a  portion of the wall of its fundus to
about the  extent of a five-shilling piece was slightly more puffy than
the other  portions, and,  on cutting  into it, air-bubbles escaped.
There had been  no laceration of the placental surface; the uterine
cavity contained only one small clot;  its lining  membrane was
healthy.   The coronary vein  of the stomach was  distended ; the
right side  of the heart was slightly  gorged,  and when the auricle
was punctured air-bubbles escaped with the blood which it contained,

   Davidson2 reports the case of  a Hindoo woman who was
admitted  into the Kaira Gaol  Hospital and safely delivered of a
female  child.   The labor was in  every respect normal.  The
placenta came away at  the  usual  time, and there was no post-
partum hemorrhage.  About three-quarters of an hour afterward
the woman died without any apparent  cause.   There had been
no hemorrhage or convulsions.  The patient had been taking
some nourishment when  she suddenly fell back and expired.
At  the  post-mortem examination two  hours  after death the
uterus was found empty, with large and  somewhat distended
veins; the right side of the  heart  contained  a quantity of air
mixed and churned  up with blood, which escaped  in bubbles,
1 St. George's Hosp. Reports, vol. vi.
8 The Lancet, vol. i. p. 999, 1883. 
62
the lungs  were congested; all  the other organs were normal.
The most interesting and convincing case is related by Olshausen.
It is  the most  convincing  on  account of  the painstaking and
accurate post-mortem examination which was made to determine
the cause of death.1

  A robust secundipara, aged 29, was delivered at full  term.   The
uterus was unusually distended ;  no albumen in urine.   The  labor
was lingering and  the uterine douche was used.   The water was of
300 R. and was forced into the vagina gently by a pump.   A third
injection was made by a  midwife.  After eight minutes'  use  the
patient began to complain of oppression.  The tube was withdrawn.
The patient rose in bed, immediately fell back senseless, and died
in less than a minute under convulsive respiratory movements and
distortion of the face.  Eight minutes later bleeding by the median
vein was tried,  but only a few  drops flowed.   On touching  the
body  distinct and widespread crepitation  was  felt.
  Autopsy eight hours after death.—A large quantity of dark fluid
blood escaped  from the sinuses  of the dura  mater. The cerebral
membranes very hyperaemic ;  brain  normal,  lungs somewhat con-
gested, heart lying transversely,  apex  in fourth  intercostal space.
Left ventricle in firm contraction, right quite soft, something like an
intestine  with thick walls ; the coronary vessels contained a quantity
of air  bubbles.  Left heart contained  only a small quantity of blood ;
the right held little, but it was frothy.  The distended uterus crepi-
tated  everywhere  on  pressure under the  hand.  A number  of
subperitoneal  vessels  of medium  size  were  plainly filled  with
air.   The  right broad ligament was strongly distended with  air
bubbles, and this  emphysema of cellular tissue extended  from the
broad ligament through the retro-peritoneal space to the  inner side
of the right kidney, and even  below the liver to the inferior vena
cava.   The inferior vena cava was enormously distended—it was  at
least an  inch in diameter—containing mostly air.  The uterus  was
divided in the median line; a placenta was attached to the anterior
wall;  a small flap  was detached from the uterus, a second placenta
was attached behind and to the right;  a  larger portion of  this  had
been separated, so that there was a sort of a  pouch between it  and

  1 Monatsschrift f. Geburtskunde, Jan. 1865.  American Journ. Med. Sciences,
July, 1S65. 
63
 the  anterior wall.   The  two ova were  uninjured.   The  air had
 gained access into the veins at the placental site.   It was concluded
 that the tube had  been passed into the uterine cavity and that air
 had been thrown in with the water by the pump.

   It would be difficult to conceive in what manner air could be
 drawn into  the  uterine  veins by the aspiratory movements of
 the  chest or heart, as is  the  case in the veins about the apex of
 the  chest.   Another  explanation must be sought for, and this
 will be found in the change of structure, and the relations of the
 uterine veins.  The veins during pregnancy keep pace with the
 enormous physiological  hyperplasia of the  uterine tissues, and
 are  gradually converted  into large  sinuses, more especially the
 vessels at the placental  site;  they are simply excavations or
 channels in the contractile  muscular walls of the uterus, their
 size being  subject to the state of the uterine walls, whether at
 rest, relaxation, or contraction.  When  the placenta is detached,
 some of these sinuses are laid open, and in a normal condition
 their calibre is obliterated by the contractions of the uterus and
 the  formation of thrombi.  If, from any cause, air should reach
 the  uterine cavity, it may be aspirated  into the uterine sinuses
 by relaxation of  the  uterine contractions,  and, having gained
 access into them, it is readily forced into the circulation by sub-
 sequent contractions;  the uterine walls acting the  part of a
 suction and forcing-pump.  During forcible uterine contractions
 the veins are nearly emptied  of their contents, and, as  the organ
 relaxes, the walls of the  veins are distended and  a vacuum is
 formed, which is filled with blood or air.  Should the relaxation
 be slow, the empty spaces are readily filled with blood or serum
 in the absence of  air, but if  the uterus  relaxes quickly the suc-
 tion  power  is proportionately greater, and, in the event air  has
 reached the  uterine cavity, it is  aspirated into  the open veins,
 and, by reaching  the right side of the  heart through the vena
 cava, it gives rise to the  same train  of  symptoms as when it is
 admitted into a vein during a surgical operation in the regions
of the neck. 
64
  Pulmonary Vein.  Dumin's case.1  This is the only case on record
where it is claimed  that death was produced by the entrance of air
from a pulmonary  tubercular  cavity through  the  pulmonary vein
into the left side of  the heart.  The  patient was a young man suffer-
ing from pulmonary tuberculosis in the last stage.  Physical diag-
nosis revealed a large cavity in  the  apex of the right  lung.  After
the patient  had been in the hospital for  three weeks the general
conditions  remained  about  the same,  while  the  local  destructive
process  had been progressing.   One day, after eating his dinner,
he arose from  his bed, fell down, and expired almost instantly with-
out uttering a word or  sound.  At  the post-mortem  examination,
twenty-four  hours after death, it was found that the apex of the lung
contained a cavity  of considerable  size,  besides  extensive  crude
infiltrations.   The left lung  contained numerous nodules and three
small cavities.   The third cavity in the substance and near the base
of the  lung contained a small  amount of blood  intimately  mixed
with air-bubbles.  The heart was slightly dilated.  The left ven-
tricle  was filled with  blood mixed with innumerable  small  air-
bubbles.   The right cavity also contained air, but in much lesser
quantity.  All the larger arteries contained air mixed with blood ;
air-bubbles were also found  in the venae cavae and the pulmonary
artery.  The arteries  and veins in  the brain  and meninges were
found distended almost  exclusively with air.  No signs of advanced
putrefaction could be found, and none of the parenchymatous organs
contained gases.  The reporter explained  the sudden death by the
entrance  of air from  the small cavity  in the left lung, which con-
tained spumous  blood, the air having  found  its way into an open
branch of the  pulmonary vein, and from thence into the  left side of
the heart.   The air, which was found  in the right side of the heart
and veins, according to his view, had passed  through the systemic
capillaries.   As  the direct cause of death, anaemia of the brain  is
mentioned.

  Remarks.—It seems to  me that  several reasons  might  be
mentioned which would throw doubt on the correctness of the
assertion that, in this  case, the immediate cause of death was
owing to entrance of air into the pulmonary vein.   i. The time
which  had  elapsed from the commencement of the attack until
1 Berliner Klin. Wochenschrift, January 30, 1882. 
65
death  took place was not  sufficient to produce  such an exten-
sive distribution of air, unless it could be proved  that the heart's
action continued after respiration had ceased.  2. The existence
of an open vessel in any of the cavities was  not proven at the
examination after death.   3.  The body appears to have  been
affected by a certain  amount of putrefaction, which  may  have
been sufficient,  in degree, to give  rise to the evolution of gases,
and the putrefactive changes may have been limited to, or were
at least farthest advanced in, the blood, which would explain the
absence of gas  in any other part of the body, except  within the
bloodvessels.   4.  Snycope is a frequent cause of sudden death
in greatly debilitated  patients when the heart is called  upon to
perform an  increased  amount of labor, as  when  the  patient
suddenly assumes the erect position.

  Superior Longitudinal Sinus.  Volkmann's case.1  The only fatal
case of admission of air into the sinuses of the dura mater is  reported
by Genzmer.  The patient was a female, 63 years of age,  who was
affected with a perforating sarcoma  of the dura mater.   The tumor
was noticed about  two years before the operation,  and was located
in the  region of the posterior extremity of the  sagittal suture, and
for a long time gave rise to no  inconvenience.  For the last six
months it caused intense headache.  On  one occasion, a physician
believing that it  was  an atheroma, attempted  its  removal, but as the
first incision gave rise to copious hemorrhage, he desisted from any
further attempts, and the wound healed kindly.  When the patient
was admitted under Volkmann's care into the Clinic at Halle, the
tumor  presented a lobulated appearance, being composed  of  three
parts, each  about  the  size of  a plum, and  was located over the
posterior extremity of the sagittal suture.   On touch, the tumor was
soft and elastic, and imparted  to the finger  distinct  pulsations.
Gradual compression reduced its  size one-half;  when the  pressure
was discontinued it resumed its further dimensions.   On ausculta-
tion, a  blowing sound was heard synchronous with the radial pulse.
By pressing the  end  of the index finger deeply between the  lobes
of the tumor, a bony defect in  the skull was readily detected.  The
conclusion  was reached, that the  tumor had  sprung from  the dura

   1 Verhancllungen d. Deutschen Gesellschaft f. Chirurgie, vol. vi. p. 32.
       5 
66
mater, and  had perforated  the  skull by  the  prolonged pressure,
causing interstitial absorption of the cranial  vault.   During  the
patient's stay  in the hospital the tumor increased very rapidly in
size.  As no brain symptoms were present, it was assumed that  the
substance of the brain was intact.  In view of the speedy fatal issue,
which of necessity would take place  without operative interference,
Volkmann decided to remove the tumor.  The operation was done
April 2, 1875.  Under strict antiseptic  precautions the tumor was
exposed by a crucial incision, and the flaps reflected with the peri-
osteum  to the margins of the opening in  the skull.  The aperture
in the bone measured  5-^ by 4^ cm. in  diameter.   With a  Luer's
cutting forceps the opening was enlarged to 7 by 8 cm.  The tumor,
when exposed, was nearly as large as a fist, and firmly  adherent to
the dura mater.  The dura mater was carefully divided around  the
margins of the tumor, which had now been liberated  from  all  its
attachments except the falx cerebri.  It  was  now drawn forward
through the opening in the  skull, and the falx  cerebri divided with
scissors from before backwards.  This  step of the  operation was
attended by alarming hemorrhage.  As the blood was being sponged
away to expose momentarily the field of operation, a peculiar and
characteristic  lapping  sound was heard, which  indicated  to  all
present  that air had entered  the longitudinal sinus.  At the same
time the assistant, Avho  was giving the chloroform, remarked,  "She
is  dying."   The wound was  immediately  compressed with a large
carbolized sponge.  The patient was in collapse, her breathing was
interrupted and stertorous.   After a short  pause, it was determined
to complete  the operation,  but as  soon  as the tumor was  again
drawn forward, and its attachment  at the junction of the longitu-
dinal with  the transverse sinuses was divided, air again  entered,
accompanied by the same characteristic sound.   The  tumor was
separated  rapidly  from its  remaining  attachments, and  a  Lister
dressing was applied in such a manner as to make at  the same time
a requisite amount of compression for the double purpose of  arrest-
ing hemorrhage and preventing further ingress of air.  At this time
the patient was pulseless, pupils dilated,  extremities cold and blue.
Auto-transfusion,  by constricting the arms and  legs  with  elastic
bandages, had  the effect of  momentarily stimulating  the heart,  but
respiration became more irregular and interrupted, and  after a  few
more brief moments the patient died.  At the post-mortem exami-
nation, which was  held on the following day, the right side  of  the 
67
 heart was  opened under water, air-bubbles escaped, showing con-
 clusively that air  had made its entrance  through  the longitudinal
 sinus.  The left side of the  heart contained  no air.   Air was  also
 found in the pulmonary artery and the subpleural vessels.  The left
 side of the brain had suffered more from compression by the tumor
 than the right.  The defect in the dura mater corresponded to the
 opening in the skull.  An additional source of hemorrhage  was
 detected at the posterior margin of the defect in the cranium, where
 the opening of a vein in the substance  of  the bone,  5 mm. in
 diameter, could be seen.  Under the microscope the  tumor showed
 small spindle-shaped cells, with  a very vascular intercellular sub-
 stance.

   Remarks.—In this case all circumstances favored the entrance
 of air into the wounded  sinus.   The sudden and  severe loss of
 blood from such a large  reservoir as the  longitudinal sinus
 rendered  the  vessel empty, thus  creating  the  most essential
 element in the causation of air  aspiration.  The position of the
 patient during the  operation undoubtedly was such that  the
 force of gravitation assisted  materially in the  formation of  a
 vacuum.   The walls of the sinus being rigid and attached to
 the surrounding structures prevented collapse  of the vessel,  and
 held  the wound patulous.  That death was owing to the intro-
 duction of air is sufficiently proven by the symptoms during life
 and the evidences derived from  the post-mortem examination.
   Veins of Dipld':.   Franck1 asserts that he has repeatedly seen
 aspiration  of air  into the veins of the diploe after trephining.
 He claims that the air  reaches  the  heart through the medium
 of the vertebral veins, which, from  their protected position, are
 more favorably located for this purpose.   By experiments he
 proved  that ligation of the jugular veins does not prevent  the
 aspiration  of air through  the veins of the diploe, while, on  the
 other hand, this  accident cannot  happen  when the vertebral
 veins are  compressed.   As the veins of the diploe  in  some
 instances are unusually large, and their walls firmly attached to

  1 Sur la transmission de l'aspiration thoracique jusqu' aux canaux veineux des
os du crane, etc.  Gazette Med.,  No. 25, 1881. 
68
the unyielding bone tissue they constitute channels which can-
not contract in  the event they  are  injured, consequently we
should a priori expect that aspiration  of air will take place
under the same circumstances  as in  the case of the  sinuses of
the dura mater, and in all extensive injuries of the cranial bones
the same  caution should be exercised  to guard  against this
accident.  In troublesome  hemorrhage from venous sinuses  in
bone, the bleeding is promptly and safely arrested by implanta-
tion of an aseptic sponge, which can be left in situ, as it will be
removed by the granulation tissue during cicatrization.  In  such
instances the sponge is peculiarly well adapted, as the lumen of
the vessel is surrounded by  unyielding bony walls, which will
support any amount of pressure on part of the aseptic tampon.

          XL Experiments on  Venous Air-Embolism.

   The injection of air was always made into the jugular  vein.
The neck was  shaved, and the surface  disinfected with a five
per cent, solution of carbolic acid.  Ether was always used  as
an  anaesthetic, the animal being  kept fully under  its  influence
until everything was in readiness to thrown in the air, when the
inhalation was suspended, and the animal was allowed to come
out from  under its influence, for  the  purpose  of studying the
effects of the air on the heart and respiration, independently of
the effects of the  anaesthetic.  The vessel was  freely exposed,
usually  in the  lower part  of the neck, by a parallel incision.
After isolating it to the extent of from two  to four inches, the
influence of the respiratory movements of the  chest  on the
venous circulation was  carefully studied.  Then a haemostatic
forceps was  applied to the distal portion of the vein.  Below the
point of compression  the  blood was forced out of  the vessel
between  two  fingers,  and its  return prevented by  applying
another pair of forceps to the proximal end of the exposed vein.
We had thus a bloodless  portion of vein between the forceps,
presenting a ribbon-like band.  This was partially divided  in an
oblique direction for the purpose of facilitating the introduction
of a canula.  The canula was securely fastened in the vein by a 
69
 ligature, when the proximal  pair of forceps were removed, and,
 by compressing the bulb, the  air was  injected with force, so as
 to imitate as nearly as possible the conditions present during
 the  accidental  introduction of air.  The canula was connected
 with a rubber-bulb, of known capacity, by means  of a rubber-
 tube.   After the completion of the experiment (if the animal
 survived) the vessel was divided completely, and both ends liga-
 tured with catgut, and  the wound closed with a continued catgut
 suture.  The weight of the animal and amount of air  injected
 were estimated accurately in most  instances.

   Experiment No.  i.—Sheep, weighing  120 pounds.  Left jugular
 vein.  The vessel was opened  in its lower third, but no air entered.
 A rubber-tube was  introduced for a distance of two inches with a
 view of facilitating the  spontaneous ingress of air, but this accident
 failed  to occur.   Air was injected, at intervals  of eight minutes, in
 quantities of 30 c. cm  each, until the  enormous amount of 480 c. cm.
 had  been introduced.  After the first injection nothing was observed
 that indicated the presence of air in the veins or the heart.  After
 the second dose a  slight splashing  sound could be heard  over the
 cardiac region,  which  became  louder and  more  distinct as the
 amount of air in the right side of  the heart increased.   The first
 serious symptoms observed were a  tumultuous  action of the heart
 and  difficulty in breathing, which  became  aggravated by every
 succeeding injection.   Towards the end  of the experiment, which
 lasted  nearly two hours, the animal was attacked, at short intervals,
 by general convulsive movements.  After the suspension of respira-
 tion  the heart's  action  became very slow and feeble, and  at times
 irregular.    The immediate cause  of death  was plainly due to
 asphyxia,  as  manifested by the great dyspnoea and  the  cyanotic
 hue of all visible mucous surfaces.   On examination after  death, a
 few air-bubbles and only a  small amount  of dark blood were found
 in the  left ventricle.  The right ventricle was arrested in the diastole
and contained a  large quantity of very dark, almost black,  spumous
blood.  Air-bubbles were found in a number of distant arteries of
small size.

  Experiment No. 2.—Adult, large cat.   In this instance the canula
was introduced and tied in the  left  jugular vein.   The heart was 
70
exposed  before  the  injection was  made with  a view of observing
directly the effects produced by sudden inflation of the right cavities
of the heart.  Before the air was introduced, the  heart contracted
regularly—artificial respirations being made for the purpose of pre-
venting death  by asphyxia.   As soon as the right side of  the  heart
was distended  by the air, the left auricle and both  ventricles ceased
to contract, while the right auricle continued to pulsate.  The pul-
sations  were  feeble  and  irregular.   The  coronary veins  became
filied with air-bubbles, presenting the appearance of a rosary.  On
opening the superior vena cava, air and frothy blood  escaped, the
right side of the  heart collapsed and all  chambers of the heart  com-
menced to contract regularly and with considerable  force.   The
pulsations continued for 15-20 minutes, becoming more feeble and
irregular and  intermittent towards the  last.   After death,  air was
found  in both venae cavae and the iliac veins.  The left ventricle
was completely empty.   In this case,  owing to the small size of the
heart and the  large  amount of air  introduced, the contractions of
the right ventricle were arrested in the  diastole, while respiration
continued.   Death took  place suddenly from mechanical  over-dis-
tension of the heart.

  Experiment No. 3.—Dog, weight 65 pounds.  Injected 30 c. cm.
of air into left jugular vein.   Churning sounds over cardiac region
loud and  distinct.   Heart's  action became  very  tumultuous  and
intermittent.   Respirations superficial and  rapid.  The animal was
bled from the distal  end of  the  jugular vein to the amount  of  four
ounces, whereupon the heart's action became regular and the respi-
rations diminished in frequency.  The vein was divided completely
and both ends were tied with fine catgut ligatures, the wound being
closed in the usual manner.   For a number of days the dog appeared
quite unwell, showed no disposition to eat and  acted very stupidly,
being inclined  to sleep most of the time.   Subsequently he recovered
completely.   In  this case the intravascular pressure was  promptly
relieved by free  bleeding which enabled the  heart to force the air
through the pulmonary into  the general circulation.   The stupid
condition of the animal  was undoubtedly owing to embolism of the
cerebral vessels,  which disappeared after the disappearance of the
air-emboli by absorption.

  Experiment No. 4.—Adult, medium-sized cat.  Injected 15 c. cm.
of air into left  jugular  vein.   Heart's action arrested  at once. 
7i
Respirations which  were  irregular ceased a  few moments  later.
The chest was opened at once.  The  right side of the heart was
found enormously dilated  and almost motionless.  Coronary veins
filled with air.   The right ventricle was punctured with the needle
of an aspirator and its contents withdrawn,  when the  pulsations
were re-established.   The ventricle was again  inflated  through the
needle of the aspirator.  Five minutes after this injection the pulsa-
tions numbered about 250 per minute.   Five minutes  later the left
auricle ceased to contract, the'movements of the  right being irregu-
lar and about  80 to the minute.   After the lapse of another five
minutes the pulsations of  the ventricles were only 17 a minute and
a little later all  movements ceased.  This experiment demonstrates
that  the  arrest  of the heart's action was due to  mechanical  over-
distension,  as  aspiration of  the right ventricle  was  followed  by
regular and strong  contractions  in all  cavities of the heart.   The
contractions were not the result of the mere mechanical  irritation
of the heart by the puncture, as other and equally severe irritants
were previously applied without producing any effect.

  Experiment No. 5.—Dog, weight 35 pounds.   Before operation,
respirations 40, pulse  140.  Injected 20 c. cm.  of air into  right
jugular vein.   Convulsions  followed which lasted for  about two
minutes.   Respiration rapid and stertorous.   Pulse 300.   After five
minutes the animal made repeated attempts to get up and walk, but
invariably fell down on account of  imperfect control over the move-
ments, or paralysis of the posterior  extremities.    Half an hour later
the animal  was able  to walk, but  appeared very feeble.   Pulse 120,
respirations  somewhat accelerated.  Recovery was complete.  In
this case  the equilibrium of the circulation was soon restored and
the air in the right side of the heart passed through the  pulmonary
into  the general circulation in a very short time, as was evident from
the presence of symptoms  indicative of embolism of some of the
vessels in the cerebro-spinal centres.

  Experiment No. 6.—Dog, weight 75 pounds.   Injected 60 c. cm.
of air into the right jugular vein.   Churning sounds loud  and dis-
tinct; heart's action  labored.   Respirations exceedingly rapid, later
stertorous.   The  animal recovered  rapidly  from  the  immediate
effects of the  air-embolism,  and was soon as well as  before the
operation. 
72
  Remarks.—These experiments  tend to  prove the following
statements: I.  A small amount of air in the right side of the
heart in  a healthy animal  gives rise only to temporary symp-
toms referable  to the heart's  action and the pulmonary circu-
lation.  2. When air has been introduced into the right side of the
heart in such quantities as not to arrest the contractions of the
heart at once, it is forced through the pulmonary capillaries into
the left side of  the heart by the contractions of the right ventri-
cle.  3. The danger attending the insufflation of air into veins is
proportionate to the amount of air introduced, as well as to the
capacity  of the right ventricle to resist intra-cardiac  pressure.
4. When a fatal dose of air has been introduced into the venous
circulation, death  takes  place almost instantaneously from arrest
of the heart's action, or later from  suffocation.  5. Spontaneous
ingress of air  into a  wounded,  healthy jugular  vein  never
occurred in these  experiments and must be considered almost a
physical impossibility, as the resilient walls of the wounded vein
collapse readily when  exposed to atmospheric pressure.
  Dogs weighing  about 30 pounds would usually recover in  a
short time after an injection of 30 c. cm. of air, while double that
amount constituted generally a fatal dose.   Sheep  required  a
proportionally  larger  dose  to produce a  fatal result.   These
experiments  also tend to prove that  animals of the same kind
and species do  not manifest the same degree of tolerance to the
presence of air in veins. Young animals succumb more readily
to its effects; in the adult animal the degree of tolerance depends
on the development and contractile power of the right ventricle.
In all cases where life was prolonged for a considerable length of
time after the injection of air was made, and the ventricular con-
tractions were not much impaired, bubbles of air were found in
the left side of  the heart, showing conclusively that the air must
have passed from the  right ventricle through  the  pulmonary
capillaries.  In experiments Nos. 3 and 5 the well-marked cere-
bral disturbances  were undoubtedly produced by secondary air-
embolism of the vessels of the brain and spinal cord, since these
disturbances disappeared  after the removal  of the  emboli by
absorption.   When the same amount of air was administered in 
73
 one dose, it always  proved more dangerous than when injected
 in divided doses, which  simply means, that during  the interval
 between the injections sufficient time had elapsed for the right
 ventricle to force at least a portion of air through the pulmonary
 capillaries into  the  general circulation ;  thus preventing for a
 time at least a fatal degree of intra-cardiac pressure.  The greater
 the development of  the  right ventricle, the  greater the tolerance
 of the animal to the presence of air in veins.  This  statement is
 well exemplified by the fact that in horses a larger amount of
 air is required to produce death, while in dogs a proportionately
 much smaller dose will  result  in death.   This is because in the
 former  animals  the right ventricle, from  its proportionately
 greater strength, is  more competent to  perform an additional
 task.  If death followed  immediately after the injection, the dose
 was usually a large one, the heart's action  having been suspended
 before respiration ceased, and on post-mortem examination the
 right ventricle  and  auricle were always found over-distended
 and tympanitic, containing a moderate  amount of blood not
 intimately mixed with a large amount of air, while  the left side
 of the heart was nearly or completely empty. If death occurred
 some time  after the  injection, great dyspnoea was observed,
 lividity of the  mucous membranes, tumultuous action  of the
 heart, and respiration  ceased  prior to cessation of the action ot
 the  heart, showing  conclusively  that death took  place from
 carbonic acid intoxication.  In these cases the necropsy revealed
 a lesser degree of distension of the right  chambers of the heart,
 which  invariably contained spumous blood or blood intimately
 mixed with air.  The  pulmonary artery  and its branches were
 filled with air  and  spumous  blood,  and bubbles of air  and a
 small quantity of blood were present in  the left ventricle.  In
 opening the jugular vein I  have always noticed that the vessel
 would  promptly collapse as soon as hemorrhage ceased, being
transformed into a pale, round cord, in which  the wound could
be found only with great  difficulty.   Air was never seen to
enter, even if the wound and a portion  of the vein were kept
patent with forceps or  a  rubber-tube.  I frequently arrested the
column of blood in the vein by applying  a  compressing forceps 
74
above, and opening  the vessel below, thus creating a favorable
condition  for the  spontaneous  entrance of air,  but  the result
remained  the same.   It is therefore only reasonable to assume,
that air will enter spontaneously only in case a vein near  the
heart is wounded, the walls of which  are  prevented from col-
lapsing  by fixations  of its tunics  to adjacent, unyielding struc-
tures,  or  in case  the vein walls themselves have  lost their
resiliency by previous pathological changes.

         XII.  Experiments on Arterial Air-Embolism.

  Experiment No. i.—Medium sized dog.   The left carotid artery
was exposed and isolated, and two haemostatic forceps applied about
two inches apart.   The artery was divided between them, and  the
proximal end secured by a  ligature.  Into the distal end the canula
of the injecting bulb  was introduced and fastened with  a ligature.
When  the  animal had  fully  recovered  from the  anaesthetic,  the
forceps were removed, and 80 c. cm. of air were injected at once and
with considerable force; the canula was then removed and the artery
ligated.   The animal  collapsed almost instantaneously, and respira-
tion was suspended  for nearly two minutes.  The animal appeared
motionless  and  in a condition of profound stupor.   Heart's action
tumultuous and  very rapid.   Two minutes after the injection churn-
ing sounds were audible over the cardiac region.   When respira-
tion was re established the  movements of the chest were slow and
irregular, gradually becoming slower and  slower until, after about
fifty attempts, they ceased entirely.  The limbs were rigid, and  the
trunk  in a position of opisthotonos.  The heart  continued  to con-
tract for about two minutes after respiration had ceased.  All vessels
leading  to and from the heart were carefully ligated, and the organ
removed and examined under water.  The coronary  veins contained
bubbles of  air.   All cavities of the heart  contained  air, the largest
amount  being found in  the left auricle.   Coagula were  present  in
all of the chambers, except in the left auricle.  The circle of Willis
was distended with  air,  as were many of  the smaller vessels  of the
brain and its membranes.   The cerebral vessels  were  gorged with
dark blood.  The air  injected into the carotid artery had evidently
passed directly through the cerebral capillaries into  the venous cir-
culation, giving rise to venous and  general air-embolism.   In the 
75
 beginning respiration was immediately suspended from temporary
 suspension  of  innervation, but was  re-established  as  soon as the
 amount of  air  in the cerebral  vessels had  lessened sufficiently to
 allow a better  blood supply.  It, however,  ceased definitely under
 symptoms expressive of extensive embolism of the pulmonary artery.

   Experiment  No.  2.—Sheep, weight  90  pounds.    Left  carotid
 artery prepared  as  in  previous experiment, only that the air was
 injected in  a central direction, towards the heart. After the animal
 had recovered  almost completely from the effects of the anaesthetic,
 150 c. cm.  of  air were thrown  in,  and the proximal end of the
 artery was  tied.   The animal was  at once thrown  into  a tetanic
 state, with  rigid  limbs and retracted  neck.   All reflex movements
 and sensations  were completely suspended.  The heart's action was
 irregular, tumultuous, and over the cardiac region distinct churning
 sounds were heard.   Respirations exceedingly rapid.   The mucous
 membranes accessible  to sight presented  a strikingly  pale  and
 anaemic  appearance.   Death occurred in fifteen minutes, respira-
 tion ceasing first.   Examination  immediately after death showed
 the right ventricle greatly distended and  tympanitic on percussion.
 It contained spumous  blood, air, and a few small coagula.  Left
 ventricle  contained  only a minute  quantity  of spumous blood  and
 fine blood  clots  adherent to the endocardium.   Air-emboli  were
 found in almost all vessels throughout the body.   Coronary arteries
 distended with air.   Jugular veins contained more air  than blood.
 Basilar  artery  and  superior longitudinal sinus  contained a large
 amount of  air.  The tongue and  other distant  organs extremely
 anaemic.  Although this  large quantity of air was thrown directly
 into one of  the large arteries, it was forced into the  smallest vessels
 and  through the  capillaries into the veins and the right side of the
 heart by the powerful contractions of the left ventricle, giving  ori-
 gin to a combination of symptoms arising from arterial and venous
 embolism.   Death was  finally produced in  a similar manner  as if
 air had  been injected directly into the veins.  Some of the air had
 passed all the capillaries and was found in the left side of the heart.

   Experiment  No.  3.—Medium sized adult cat.  With a view to
ascertain how  soon  air would pass  through the capillary  vessels
after injecting  it into the carotid artery, the  jugular  vein on  the
opposite  side was opened before the injection  of  air was made. 
                              76

About  15 c. cm.  of  air were  thrown into the carotid  artery in a
peripheral  direction.   The animal  was  immediately seized with
convulsions and died  in  less  than a minute.  Respiration ceased
first.  Air was seen to escape from  the wound  in the jugular vein,
and was also found in nearly all of the vessels throughout the body.
On opening the chest the right side of the heart was found distended
to its utmost, and  tympanitic  on percussion.   The contractions of
the right auricle were twice as  rapid as the ventricular contractions.
The  movements of the left auricle were the same  in frequency as
the ventricular pulsations.   The left auricle ceased to contract seven
minutes after death.   The right ventricle was punctured with the
needle of  an aspirator, and its  contents  removed, whereupon the
contractions became much stronger.
8 minutes after death ventricles contracted 44 times a minute.
Then all contractions ceased and could not be restored by any kind
of irritation.
  Right  auricle  ceased  beating  ten  minutes  after death, but com-
menced  to contract again  nineteen  minutes later, contracting  24
times a minute, the  movements becoming  more  rapid and  at times
irregular for forty-eight  minutes after death.

  Experiment No. 4.—Dog, weight 35 pounds.   Into the left caro-
tid  artery 60 c. cm. of  air were  injected  in a proximal direction.
The animal was seized at once with convulsions of a tetanic charac-
ter with the limbs extended and rigid.  Involuntary discharges  from
bowels  and bladder.    Sensation,  motion, and  reflex  actions sus-
pended.   Pupils contracted.   Respirations  very rapid.   Heart's
action slow and labored.  The left jugular vein was opened and four
ounces of blood were abstracted with the result of greatly improv-
ing the heart's action.   Both vessels were ligated and  the wound
closed.   The animal was in profound stupor, resembling complete
anaesthesia, until  death  occurred  two  and a half hours after the
operation.  Half an hour after the injection the pulse was 74, respi-
rations 44 in a minute.   On opening the  abdomen the large veins
were found very much  dilated and contained air.  Large  air  bub- 
77
bles were also found in the pulmonary artery, internal mammary,
and coronary arteries.   Small thrombi  were found in many of the
ultimate branches of the pulmonary artery.   The right side of the
heart was distended with spumous  blood and air.  The left ventri-
cle was almost completely empty, the endocardial lining presenting
many patches of subserous ecchymoses.   Nearly all vessels of the
brain  and the  longitudinal  sinus  contained air.   Cerebral and
meningeal vessels  engorged  with  blood.  The  animal died  with
marked symptoms of asphyxia.   The tetanic rigidity of the extrem-
ities and  the muscles of the trunk, as well as the  remaining promi-
nent cerebral  symptoms, were  produced by the intense  cerebral
congestion, the result of obstruction of  some of the smaller vessels
by air-emboli.

   Experiment No.  5.—Adult dog,  weight  20 pounds.   Into the
peripheral end  of the  right carotid artery 20 c. cm. of air were in-
jected  after the animal  had  completely recovered from the anaes-
thetic.   The dog collapsed almost immediately and fell to  the floor,
perfectly unconscious,  with extended and rigid limbs.   Breathing
exceedingly rapid, but  gradually growing slower as consciousness
returned.   When the  animal attempted to  walk it staggered, and
frequently fell,  having  apparently lost the power of co-ordination in
the posterior extremities.   The pupils, at first dilated, later became
very much contracted.  After about two hours,  the animal walked
without difficulty, but respiration, as well as  the heart's action, con-
tinued  very rapid.   The  next  day complete recovery had taken
place.   Aside from the cerebral and spinal  symptoms, the arterial
embolism  in this  case resulted in  no serious  consequences ; the
most threatening symptoms  were  referable to venous embolism,
showing that most of the air had passed through the capillaries into
the venous circulation  and right side of the heart.

   Experiment No. 6.—Adult dog, weight 22 pounds.   Right  caro-
tid artery exposed and 45 c. cm.  of air injected towards the heart.
Involuntary discharges from  bladder and rectum.  Pupils dilated,
later contracted.   Animal completely unconscious, anterior limbs
extended and rigid, slight opisthotonos, breathing mostly abdominal.
Churning  sounds  over heart heard a  few  seconds after  injection,
disappeared after eight  minutes.  Respiration ceased  five minutes
after the air was injected, but was again restored by artificial respi- 
78
ration and  faradization  of  vagus and  diaphragm.   Twenty-three
minutes after the  injection, pulse 128, respirations  24; seventeen
minutes later, pulse 105, respirations 26;  fifty-two  minutes after
injection,  pulse 120, respirations 20;  ninety minutes after injection,
pulse 180, respirations 20.   At this time the animal  made  several
unsuccessful  attempts to rise, but relapsed  into  a comatose state,
which continued until  death fifteen  hours after the  operation.  At
the post-mortem examination the arteries contained a good  deal of
dark, almost venous blood  interspersed with bubbles of air.  Air
was found in the uterine, ovarian, iliac and  mesenteric arteries and
aorta;  also  in  both  venae  cavae,  pulmonary  artery  and  veins.
Some  of  the smallest  branches  of the pulmonary artery  were
obstructed by thrombi.  Right ventricle distended with very dark,
almost black, frothy blood.   Left ventricle firmly contracted  and
almost  empty.   Left  auricle  contained  dark,  spumous  blood.
Coronary arteries  distended with air;  internal mammary  arteries
and veins also contained it.   Air  was found  in all the cerebral
vessels and sinuses which were distended  with dark fluid  blood.
Vessels of spinal  cord were  intensely  congested and  contained
numerous  air-bubbles.   The  mucous membrane of the stomach
presented eleven points of extravasation, the largest  being circular
and one inch in diameter.   This  case presented  the most  diffuse
form  of embolism,  the emboli  being found  equally numerous and
diffuse in the arterial and venous systems.   The multiplicity  and
diffusion can be satisfactorily accounted for when we take into con-
sideration  the large amount of  air which  was injected, and the
length of time which had elapsed from the time of insufflation until
death occurred.   The post-mortem appearances plainly  indicated
that death was produced by slow asphyxia.   The primary  uncon-
sciousness and stupor were induced by the acute cerebral ischaemia;
then a short period  of consciousness  returned  as  soon as the  col-
lateral circulation  in the  brain had  become partially established,
when again the animal became comatose from carbonic acid intoxi-
cation.  The abstraction of blood relieved the threatening symptoms
attending  the arterial embolism, but failed in preventing death from
asphyxia by secondary venous embolism.
  Experiment No.  7.—Dog, weight 26 pounds.  Injected 15 c.  cm.
of air into the right carotid artery in  a peripheral direction.   The
animal had a slight convulsion and  remained unconscious for about
twenty minutes, when it rallied and was able to walk about the room 
79
 with a slightly staggering gait.   No complications followed the opera-
 tion.   In this instance the cerebral symptoms followed the  insuffla-
 tion instantly, but owing  to the small amount of air injected, they
 were only of short  duration,  the air—passing the  capillaries in a
 short time—entered the  venous  circulation  where  it  produced
 temporary disturbances in the pulmonary circulation.

   Remarks.—Injection of air into arteries produces well-marked
 and characteristic symptoms which point directly to  a disturb-
 ance in the circulation of the brain and spinal cord.   The most
 prominent  symptoms are: Convulsions,  coma, tetanic  rigidity
 of the limbs and  extensor  muscles of  the back.  The coma
 resembles complete and profound anaesthesia.   These symptoms
 follow the operation  more quickly if the injection  is made in a
 peripheral direction toward the brain.  If the  animal  does not
 succumb to the primary effect of the air. upon  the brain and
 medulla  oblongata,  a   series   of  symptoms  succeed  which
 announce the arrival of  air in  the  veins  and  right side of the
 heart.  All of the experiments show that  it only requires a few
 seconds  for the powerful contractions  of the left ventricle to
 force at least a  large portion of the air  through the capillaries
 into the  veins.   The primary effect of embolism of the vessels
 of the brain is to produce acute cerebral ischaemia, the intensity
 of which depends upon the number and size of the vessels which
 have become obstructed by the air-emboli.   This anaemia soon
 gives rise to intense engorgement of the  collateral vessels, and
 the vessels behind  the  point of obstruction, an engorgement to
 such  an  extent,  that it often  leads to rupture of capillary vessels
 and  hemorrhage  into  the paravascular  tissues.   Unless  the
 amount of  air  injected  is sufficient to prove  rapidly fatal by
 causing suspension of functions of the cerebro-spinal centres, the
 animal dies of asphyxia  from embolism of the pulmonary artery,
 the same as  though the  air  had been  injected directly into the
 veins.  The left ventricle, from its  greater thickness  and con-
 sequently more powerful contractions (as compared  with  the
 right ventricle), is better adapted  to overcome  the  increased
resistance, and  hence  the  air  is  rapidly  forced through  the
systemic capillary  circulation into  the veins and right  side of 
8o
the heart.  On this account an equal amount of air injected into
arteries is not so dangerous as when introduced directly into veins.
as a certain percentage of it never reaches the veins and right
side of the heart.   Arterial  air-embolism  is  attended  by  an
additional  source of  danger, which  consists in  the greater
tendency to  coagulation of blood in  the heart and vessels, as
was noted  in several experiments.

         XIII. Direct Intra-Cardiac Insufflation of Air.

   These experiments  were made  with a view  of demonstrating
by ocular inspection, that sudden  over-distension of the cardiac
muscles  will  arrest their  contractility and will thus produce
paralysis of the heart  in the diastole.

   Experiment No. i.—Medium sized cat.   After  the  animal  was
fully under the influence  of ether,  respirations and heart's action
being normal, the chest was rapidly opened and the heart exposed.
Its movements remained regular.   From the sudden ingress of air
into the cavity of the chest, the left lung collapsed, and it was found
necessary, in order  to  prevent  asphyxia, to make artificial respira-
tions on the right side of the chest.   The pericardium having been
opened, the right ventricle  was punctured  with  the needle of an
aspirator, and air injected  in sufficient quantity to distend the right
chambers of the heart, which immediately ceased to contract.  On
emptying the right ventricle by withdrawing the  air and blood, the
rhythmic movements of the organ were restored.  These manipu-
lations were repeated at least half a dozen times, and  always with
the same uniform and constant results.  Half an  hour after opening
the chest all movements of the heart ceased.  The  heart was now
removed and immersed in water at a temperature of 1050 F., when
it  again commenced to pulsate at  the rate of 120 beats per minute.
After the lapse of about two minutes it was removed from the warm
water, still  pulsating, and transferred to cold water, when  all move-
ments  ceased instantaneously, and all efforts to revive them proved
futile.

   Experiment No. 2.—Large Maltese cat.   Heart  exposed, right
ventricle punctured, and 11 c. cm. of air injected with the result of 
8i
 immediately arresting the pulsations of the right ventricle.   When
 the air was withdrawn, the regular movements were renewed.  This
 experiment was  repeated on both ventricles  eight or ten times in
 the course of half an hour with  the  same results.   The auricles
 during all this time continued  to contract.  Ten  minutes after the
 last puncture and evacuation the ventricles were still pulsating.

   Remarks.—Both of these observations support the statement
 that sudden over-distension of any of the  cavities of the heart
 by inflation with  air, will  arrest its  movements in the diastole,
 and that upon the removal of the increased  intra-cardiac pres-
 sure, the movements of the  organ are restored.  It was found
 that by continuing the injecting force  after  the  right ventricle
 had become distended, air could be forced readily through the
 pulmonary capillaries into the left side of the  heart.  In some
 instances one of the cavities of the heart was kept over-distended
 and at  rest for  at least  a minute, and yet on  removing its con-
 tents the rhythmic movements were resumed.

     XIV. Aspiration of Right Ventricle for Air-Embolism.

   Being satisfied of  the fact  that sudden over-distension of the
 right ventricle may and does  produce paralysis  in the diastole,
 it appeared  reasonable to resort to some direct measure in
 removing the cause of over-distension  in grave cases of venous
 air-embolism.   Puncturing and  aspiration of the right ventricle
 seemed to offer the best chances for accomplishing  this object.
 In the following experiments  artificial venous air-embolism was
 produced in the usual way, when the right ventricle was  punc-
 tured with the needle of an aspirator two millimetres in diameter,
 and the contents of the right  side of the heart removed by aspi-
 ration.  The region over the  heart was shaved and  disinfected,
 and  the exact point of  puncture located before the animal was
anaesthetized.  The needle was always  carefully disinfected by
passing it through the flame of an alcohol lamp, and immersion
in carbolized water.   When the puncture was made, the needle
was  advanced first only sufficiently deep  to bury the opening
in its point beneath the tissues,  when a vacuum was  created
       6 
82
in the aspirator so that the entrance of the needle into the ven-
tricle would be promptly announced by the escape of spumous
blood.   By following this precaution, additional  injury to  the
heart,  by pushing  the  needle  further into the cavity of  the
ventricle, was  avoided, and at the same  time a prompt escape
of blood was  secured.   Experience taught me that it was very
important not to push the needle too deeply into the cavity of
the ventricle;  not only for fear of inflicting  additional injury to
the endocardial lining opposite the point of entrance, but more
particularly with a view of removing the free air which would
naturally occupy the highest point in the cavity, if it was  not
intimately  mixed with  the  blood.   The  needle was always
directed obliquely from below upwards for the twofold purpose
of making a  valvular wound in the ventricle and  of avoiding
unnecessary injury to the endocardium.

  Experiment  No. i.—Dog, weight 31 pounds.  60  c. cm.  of air
were injected  into the left jugular vein.   The animal was seized
immediately with  a  convulsion,  followed  by collapse.   Heart's
action  tumultuous.   Churning sounds over heart  were distinctly
perceptible.   Respirations rapid and superficial.  Right ventricle
was punctured, and 120 c. cm. of spumous blood were withdrawn.
Pulsations of heart became more feeble, and  as respirations had
ceased  and could not be restored, the chest was opened.  The right
ventricle was found moderately dilated and still contracting.   Slight
contractions of lower portion  of left auricle.   Left ventricle con-
tracted, but without motion.  The needle of the aspirator was then
introduced  into the right auricle, which was distended and tympa-
nitic.  After emptying it, it commenced to contract.   All contrac-
tions ceased half an hour  after the air was introduced.   Faradic
currents had no effect upon  the heart after it  had ceased  to contract.
The pericardium contained air in considerable quantity and  about
four c.  cm. of  fluid blood.  Air was found in  the right side of the
heart, the left  ventricle, coronary veins, and in the large veins in
the immediate  vicinity of the heart.   Puncture about  an inch from
septum, and nearly equidistant  between the apex and base of  heart.
No injury of endocardium on opposite side.

  Experiment No. 2.—Sheep, weight 95 pounds.  Before operation
respirations  86, pulse  140.  Injected  150  c. cm. of  air into  left 
83
 jugular vein,  which was immediately followed by convulsions and
 involuntary discharges.  Aspiration of right ventricle and removal
 of 150 c. cm.  of spumous blood.  As the animal still presented an
 asphyxiated appearance, the ligature was  removed  from the distal
 end of the jugular vein, and about 120 c. cm. of blood were allowed
 to escape.   The animal showed no signs of improvement, and died
 five minutes after the injection  was  made, having  made  only five
 attempts at respiration during the time.   Pericardium contained a
 small coagulum and a few  bubbles of  air.   Right ventricle, dis-
 tended  and tympanitic, contained spumous blood.   Two punctures
 were found over the middle of the right ventricle about one-half cm.
 apart;  the second was made during the convulsive movements of
 the animal, which necessitated a partial  withdrawal and reintroduc-
 tion of the needle.   On the inner surface  each puncture was hermeti-
 cally sealed  by a  minute thrombus  which  projected  only  very
 slightly into the cavity of the ventricle.   No injury of opposite wall
 of ventricle.  In the left ventricle, which was firmly contracted and
 empty,  a small filiform coagulum projected through the aortic orifice
 into the aorta.

   Experiment No. 3.—Old  dog, weight 40  pounds.  Injected  45
 c. cm. of air  into left jugular vein.   Churning  sounds over heart
 loud and distinct.   Heart's action labored; respirations exceedingly
 rapid.  No convulsion,  but  profound coma  and involuntary dis-
 charges.  A little more than  one minute  elapsed between the intro-
 duction of air and aspiration, during which time the heart's action
 became more and more embarrassed, and all of the symptoms be-
 came so grave, that death seemed unavoidable.   But as the needle
 reached the heart, a slight  impulse was imparted to it by the feeble
 pulsations,  and 120 c cm. of air and spumous blood were removed.
 The  heart's  action  improved   immediately, but  the  dyspnoea,
 although less  severe, was still quite prominent.   Consequently an
 additional 120 c. cm. of blood were allowed to flow  from the peri-
 pheral extremity of  the jugular  vein, which promptly relieved the
 urgent symptoms.   Ten minutes  after  the injection,  respirations
 were 240 per minute;  four minutes later  360, and  after  eight min-
utes more 120.   After forty minutes the stupor disappeared and the
animal was  able to walk.   One hour after the operation, respira-
tions were 20 and pulse 160 per minute.   At this time the animal 
84
walked  home—a distance of nearly two miles—and  subsequently
suffered no inconvenience from the  operation.

  Experiment No. 4.—Dog, weight 75 pounds.  Injected into  left
jugular  vein 90 c. cm.  of  air, which produced  intense difficulty in
breathing and profound stupor.   Sensation and reflex movements
suspended.  Heart's action exceedingly feeble and rapid.  Churn-
ing sounds distinct.   The  aspirator  and needle  were  kept in readi-
ness to be used promptly  on the  approach of symptoms  indicative
of impending death.   Two minutes after the  injection the animal
was apparently in a dying condition, when  the  needle was plunged
into the right  ventricle, and from its rapid  oscillations it  was appa-
rent that the heart's action had not entirely ceased, but  was very
rapid and feeble.  As quickly as possible 180 c. cm. of spumous
blood were withdrawn, which  promptly relieved the most  urgent
symptoms; but as the respirations still remained rapid and labored,
the ligature was removed  from  the  distal end of the  jugular vein,
and 240 c. cm. of blood  were  allowed to  escape.  Eight minutes
later after the  injection, the churning  sounds  over the heart were
still  present,  but  faint.  Respirations 144; pulse 130.  When  the
animal had recovered  from the immediate  effects of  the operation,
it was noticed that the posterior extremities could be moved only
with difficulty, the  gait being  slow and  staggering.   For  twelve
hours the animal was dull  and stupid, remaining in the same  place
without change of position.  The drowsiness  continued for  thirty-
six hours, after which the animal became lively, and went on to com-
plete recovery without  any further interruption.   In this case it was
apparent that the animal would  have died from  the large volume of
air which had been injected, but for timely use of the needle and
aspirator.   Three weeks after the experiment the animal, being in
perfect health, was killed by an arterial  injection of air.   No signs
of pericarditis, endocarditis, or myocarditis.  Puncture in ventricle
indicated by a minute faint cicatrix.

  Experiment No. 5.—Old dog, weight  25 pounds.   In  this  case
the aspirator was used a few seconds after the insufflation  of air was
made, and the result shows how important it is to withdraw the air
from the  ventricle  before it has had  time to escape into the pul-
monary artery.  Immediately after the injection of 90 c. cm. of air
into the left jugular vein, the animal became comatose.   Respiration 
85
 exceedingly  rapid  and heart's  action  imperceptible.    The right
 ventricle was punctured at once  and as soon as a part of its contents
 had been removed the impulse of the  heart was imparted to the
 needle  which could  be  distinctly seen  and  felt.   Spumous blood
 and air to the  amount  of 150  c.  cm.  were withdrawn.  The dog
 rallied  rapidly after the aspiration, being able to walk  in less than
 half an hour.   He manifested no  pain  or discomfort from the air-
 embolism or operation.   The volume of air  in this case was three
 times as large as in the previous  experiment, when  the weight of the
 animals is compared.  The immediate effects of the  air were ex-
 pended upon the  heart as was made evident by the temporary ces-
 sation of its pulsations, and yet death was prevented by the prompt
 removal of the excessive intra-cardiac pressure.  The recovery was
 more rapid than  in  the  previous cases, from  the fact  that not so
 much air had  passed into the pulmonary  artery and more  was
 removed  by aspiration.   Two  weeks  later,  the  animal being in
 perfect  health, 60  c. cm. of air  were injected into the  right jugular
 vein, which produced death in a few minutes, showing conclusively
 that the recovery af.er the first insufflation was due  to the aspiration.
 Cicatrix of puncture plainly  visible.  No signs of inflammation in
 the pericardium, endocardium, or substance of the heart.

   Experiment No. 6.—Young dog, weight 28 pounds.   In this ex-
 periment 120 c. cm. of air were thrown into  the left jugular vein in
 divided doses of 30 c. cm.  each in rapid  succession.   During the
 third injection the  animal  howled and became comatose, and imme-
 diately after the last injection  the heart's action ceased and respira-
 tions were  reduced to a few  irregular gasps.  The right ventricle
 was punctured and 120 c. cm. of spumous blood and air were with-
 drawn,  without producing  any effect  upon  the  heart.  Artificial
 respiration was  resorted to without any better result.   The chest
 was opened at once.  The pericardium  contained 4 c. cm. of dark,
 venous  blood and a few air-bubbles.   Right auricle continued to
 contract forty-eight times  per minute.   Left auricle and ventricle
 were distended  and  contained  spumous  blood.   The  needle  had
 punctured the right auricle instead of the ventricle.  All muscles,
 voluntary and involuntary, reacted  promptly to the faradic current,
but it had not the slightest effect upon the heart.

  Experiment No.  7.—Young dog,  weight  10 pounds.  Injected
45 c. cm. of air into the left jugular vein.  At the end  of injection 
86
the dog howled, and the heart's action ceased almost instantaneously.
The right ventricle was aspirated  and 60 c. cm.  of spumous blood
were  withdrawn.   Artificial  respiration  was  performed  and the
faradic current was  applied,  when  the  dog made a few ineffectual
attempts  at respiration  before he died.  On examination  the peri-
cardium  was found to contain a slight amount of dark fluid blood
and a few air-bubbles.   Both auricles  contracted about  forty-eight
times in  a minute.  Right  ventricle arrested in diastole.  Puncture
was found near base of ventricle.   Right ventricle  was again aspir-
ated,  and the faradic  current was applied directly  to the heart and
the needle,  without producing  the slightest effect.  Right ventricle
and  pulmonary  artery contained  spumous  blood.   Left  ventricle
contracted and nearly empty.

   Experiment No.  8.—Adult dog,  weight  24 pounds.   Before
operation, respirations 80; pulse 100 in a minute.  Injection of 30
c. cm.  of air into left jugular vein.   Immediately after  injection
great restlessness, dyspnoea,  and tumultuous  action of  heart.
Churning sounds  loud and  distinct.   Removed  90 c.   cm. of
spumous  blood  from  right  ventricle  by  aspiration.   After the
aspiration the  improvement in respiration and pulse was  marked.
Recovery complete, and not attended by any complications.

   Experiment No.  9.—Same  animal  as  in  experiment No. 3.
Animal  in perfect health ; time since first  operation three weeks.
Injection of 40 c. cm. of air into right jugular vein.   Symptoms the
same as before.  At the end of three minutes and a half the pulsations
of the heart ceased, and  the respirations were  nearly suspended.
The  right ventricle was now punctured  and  250 c.  cm. of  spumous
blood were removed.   No motion imparted to needle.   Faradization
and artificial respiration were  ineffectual in restoring either the heart's
action or respiration.  On  examination 30 c. cm.  of dark fluid blood
were found in  the pericardium.  No  evidences of  inflammation
from  former puncture.  Right  ventricle moderately distended with
a clot of spumous  blood.   Point of second  puncture  one-half inch
from  coronary artery.  The location of  first puncture was marked
near the  base of the right  ventricle by a faint minute cicatrix upon
the pericardial surface, while the endocardium  at  a corresponding
point showed an  old circumscribed  spot  of ecchymosis, but no
evidences of inflammation.  Left  ventricle  contained  no  air and 
87
only a minute quantity of fluid blood.  Both auricles nearly empty.
Pulmonary artery contained air and spumous blood.  This experiment
demonstrates positively and conclusively the value of early aspira-
tion of the right ventricle  in  venous air-embolism, where death is
threatened by over-distension  of the right side of the heart, or by
asphyxia.   In the  former experiment a larger amount  of air was
injected, but the animal was saved by an early aspiration by which
a large amount of air was removed before it had time to accumulate
in the pulmonary artery.  It also illustrates the utter uselessness of
resorting to any kind of mechanical  interference after a fatal dose
of air has  once passed  beyond the semilunar valves into  the pulmo-
nary artery.   In such instances the air has passed beyond our reach,
and will inevitably lead to a fatal result by asphyxia.

   Experiment No.  10.—Adult dog, weight  18 pounds.   Injection
of 60  c.  cm. of  air  into left jugular vein.   Immediate collapse;
churning  sounds  distinct.  Aspiration of 100 c. cm.  of air  and
spumous blood  from  right  ventricle.   Three  minutes after the
insufflation, respiration, and heart's  action had ceased.   No air or
blood  found  in  the  pericardium.    Needle  puncture  equidistant
between base and apex of right ventricle, and about two cm. from
septum.   Right  auricle contracting  feebly  forty times  a  minute.
Right ventricle dilated, fibrillary contractions  at apex  only; right
ventricle  and pulmonary artery  contained  spumous blood.   Left
auricle and ventricle contained only  a slight amount of  fluid blood
and a few air bubbles.

   Remarks.—These experiments serve to illustrate the following
interesting points  in pathology and surgery:  1.  The heart can
be punctured with a perfectly aseptic, medium-sized needle  of
an aspirator, without any great  immediate or remote danger.
2. Aspiration of  the right  ventricle  for venous air-embolism,
when  done early  enough (before a fatal dose  of air  has been
forced into the pulmonary artery), must  be considered  in the
light of a life-saving operation.
   Although the needle used in all  of these experiments was two
millimetres in diameter, the hemorrhage  into the pericardium
was  never sufficient in quantity to prove  a source  of danger.
The largest quantity found was 30  c. cm. (in experiment No. 9). 
88
In a number of cases no trace of blood was found in the peri-
cardium.  Against my expectations the same observations were
made in regard to air.   In one case the pericardium contained
about  60 c. cm. of air, while in most  cases  only a few isolated
air-bubbles were seen, while in  others no  trace of it  could  be
found.  In  all  cases where the  animal survived the operation
and was killed from a few days to three weeks subsequently,  no
trace of inflammation  could be found either in serous  mem-
branes, muscular  tissue, or  adjacent  organs.   Even  adhesion
between the parietal and visceral layers of the pericardium at
the point of puncture never occurred.   The point of  puncture
was  usually marked by  a faint minute cicatrix in the visceral
pericardium, unaccompanied by any pathological changes in the
substance of the heart.   We must take it for  granted that if
effusion of blood or air occurred into the pericardium in the
animals which  recovered, these  adventitious substances caused
no irritation, but were promptly removed by absorption.
  With the exception of the subject  of experiment  No. 8, it
may be safely assumed, that all of the  animals would  have died
had  aspiration  not been performed, so that the operation  saved
at least three of the animals out of ten, or  the whole number of
experiments.  The most conclusive proof of  this statement was
furnished  by the subjects of experiments Nos. 3 and 5, as these
animals died during subsequent experiments from the  introduc-
tion of a much  smaller quantity of air.  The question  naturally
arises, Why were not all of the animals, saved by the aspiration ?
In reply it  may be stated that the amount of air injected  in
most instances  was large, more  than was necessary to produce
a fatal  result.  Another element of failure consisted in  the post-
ponement of the aspiration until a fatal dose of  air had passed
beyond the reach  of the aspirator.  To prevent death by air-
embolism it is  essential to  remove the air from the right ven-
tricle as soon as possible after its entrance, before a fatal embo-
lism of  the  pulmonary artery has had time  to take place.   In
some of the  experiments a fatal result might have been  probably
prevented by removing a larger quantity of air and blood with 
8q
the aspirator, as in some instances the condition of the animal
was improved by a subsequent venesection from  the jugular
vein.

XV.  Catheterization and Aspiration of Right Auricle for Venous
                        Air-Embolism.

   In grave  cases  of accidental  air-embolism it  would  be a
desideratum  to be in possession of some means, by which  the
air could be removed directly from the right side of the heart in
the shortest possible space of time and with the simplest instru-
ment.  An aspirator is not always at  hand,  and less frequently
in a  proper  condition  to  be used on such short  notice.   It
appeared to me that inasmuch as the accidental introduction of air
usually takes place through wounds in one of the jugular veins,
a catheter  might be introduced through the wound into the vein
and from there passed directly into the heart, and through  it  the
air and spumous  blood could be withdrawn by aspiration.   A
catheter is almost always at hand, and  its introduction would
require only a few moments of time.  The following experi-
ments were made to test the feasibility of this procedure.

   Experiment No  i.—Adult  dog,  weight  24  pounds.  The right
jugular vein was opened  and 60 c. cm. of air were introduced  in the
usual way.   The  breathing became very difficult and  the heart's
action labored.   The animal  was  comatose,  pupils  dilated.   As
soon as it could be done, a number six, English scale, gum elastic
catheter, which had previously been made  aseptic, was introduced
into the wound, and passed  into the heart—a distance of  15 cm.—
and with an exhausting syringe  250 c. cm. of air and spumous blood
were removed.  The animal recovered rapidly from the immediate
effects of the  air-embolism and operation, and subsequently mani-
fested no symptoms of disease.
  Experiment No.  2.—Young dog, weight 30 pounds.  Injected
100 c. cm.  of air into left jugular vein.  The heart's action ceased
almost instantaneously.  The  same catheter was introduced and
pushed  forward a  distance of  18 cm. and about  120 c. cm. of air
and spumous  blood were withdrawn by the  mouth.   At  this time 
90
respiration ceased, and as no pulsations of the heart could be felt,
the chest was opened at once.   Fibrillary contractions of right ven-
tricle which was distended  and tympanitic.   Left auricle and ven-
tricle contracted and motionless.  Right auricle contracted regularly
80 times a minute.  Faradic and galvanic currents had no effect on
ventricles.   Right auricle responded to a galvanic  current slowly
interrupted.  The catheter was again introduced, and its course ob-
served  as it entered the right auricle.  It was found impossible  by
any manipulation to pass it from the auricle into the ventricle.   In
every instance it passed  from the right auricle directly  into the in-
ferior vena cava.  The right side of the heart was filled with water
to test  the possibility of removing fluids from the right auricle with-
out introduction of the catheter into the chamber.  A catheter with
an open extremity was used.  No amount of suction force succeeded
in removing  any of the  fluid,  until the open end of the  catheter
reached the auricle, when both  chambers could be readily emptied.
As long as the  end of the  catheter remained  in the vein, the walls
of the  vein in front of the catheter  would invariably collapse  and
close the  opening in the catheter  completely on applying  suction
force.   This satisfied me that in order to remove air or  blood from
the right side of the heart, it is necessary to introduce the catheter
as far as the auricle.   It was also evident that in  case the catheter be
introduced too  far, its distal end would pass  into the inferior vena
cava, and on aspiration only venous  blood  would be  withdrawn,
not air and spumous blood  from the right chambers of the  heart,
for the  removal of which  the procedure was intended.  On opening
the right side of the heart, a large  spongy clot of spumous  blood
was found in the right auricle, which  extended for some  distance
into the ventricle.  Left ventricle contained only a small amount of
fluid blood and a few air-bubbles.   As the heart's action had ceased
before  catheterization, death was undoubtedly due to the insufflation
of air and not to the formation  of a thrombus in the heart.

  Experiment No. 3.—Adult dog,  weight 20  pounds.   Injected 30
c. cm.  of air into right jugular vein.   Catheterization and aspiration
of right auricle, by which 90 c. cm. of air and spumous  blood were
removed when  catheter  became impermeable by a thrombus in its
interior and was removed.   Before emptying  the right side of  the
heart the animal was comatose, breathing and heart's action exceed-
ingly rapid.  After aspiration rapid  improvement and complete re- 
9i
covery.  If the catheter in this  instance had  been  permitted to
remain longer in the auricle, the thrombus which formed in the in-
terior of the instrument would undoubtedly have increased  rapidly,
and would  have extended to the auricle, in which event death from
thrombosis would  have been unavoidable.
                                              t
  Experiment No 4.—Old dog, weight 40 pounds.  Before opera-
tion respirations 16; pulse 100 per minute.   Injection  of 90  c. cm.
of air into left jugular vein.   Passed a No. 5 Nelaton's  catheter into
right  auricle,  a distance of 27 cm., and  removed 250 c. cm. of
air  and  spumous  blood.   Immediately after  the insufflation the
animal  uttered  a howl and  became comatose.   Pulse  250 per
minute, respirations so rapid that they could not be counted.  Seven
minutes  after catheterization heart's action very irregular,  tumultu-
ous, and about 300 beats per minute.   Two minutes later respira-
tion ceased, after which  the heart's action became slow and feeble,
only to cease a few seconds later.  Internal mammary and coronary
veins  filled with air.   Left  side of heart contained a small amount
of bright red,  frothy blood.  Right  ventricle  moderately dilated,
showed fibrillary  contractions.  Superior  and  inferior vena  cava,
right auricle and ventricle contained  a continuous, soft thrombus,
the oldest portion of which corresponded to the superior vena cava.
The upper  portion of  the clot  in  the inferior vena cava contained
air.  Death in this instance was due to the formation of a thrombus.

  Experiment No. 5.—Adult dog, weight 25 pounds.   Injection of
60 c. cm. of air into  left  jugular vein produced  immediate collapse,
distressing dyspnoea, and great rapidity and  irregularity of heart's
action.   The  dog howled  when  the heart's  action  ceased,  and
respiration  became gasping.  Some delay was  experienced in the
introduction of the catheter, and when the instrument  was  in  place
all signs of life had disappeared. 'About 50 c.  cm.  of  spumous
blood were withdrawn  without any signs of improvement.  Artificial
respiration  and faradization  were resorted to  without producing the
slightest  impression.    On  opening the  chest it was observed that
the right auricle contracted about 30 times a minute.   Irregular
fibrillary contractions  of apex of  right ventricle.   Right side of
heart  moderately distended with  spumous blood.   No thrombus.
Left ventricle almost empty. 
92
  Experiment No. 6.—Adult dog, weight 15 pounds.  Injection of
60 c. cm. of air into right jugular vein.   In this case the catheter
was connected with a  rubber-tube  three feet in  length, which was
kept under water; then the instrument was pushed along the jugular
vein into the right auricle.  The injection  of air was followed  by
the most urgent  and distressing  symptoms.   Only a small amount
of dark venous blood escaped through the rubber-tube until the
catheter reached the right auricle, when a gush of spumous  blood
escaped from the tube under water.  As the blood did not continue
to escape, about 60 c. cm. of spumous blood were withdrawn.  After
the aspiration the symptoms  improved rapidly, and within twenty-
five minutes, with the exception of a slight excess in the respiratory
movements, the animal appeared to be perfectly well.  The ultimate
recovery was complete and not disturbed  by any complications.

  Experiment No. 7.—Adult dog, weight  48  pounds.   Before
operation pulse 150 ; respirations 28.  Injection of 120 c. cm. of air
into right jugular vein.  The animal howled  and  collapsed.  Respi-
rations increased at once to 100 per  minute.   Heart's action tumul-
tuous, and churning sounds  loud and distinct.  Passed a Nelaton's
catheter  into the right auricle, and  aspirated 360 c. cm. of air and
spumous blood.   No signs of improvement followed, and in fifteen
minutes the animal was dead.  At the  post-mortem  examination  the
internal mammary veins were found  distended with  air.  Right side
of  heart tympanitic and distended.   Slight fibrillary contractions
of right  auricle.   Apex of right ventricle contracted regularly 22
times in a minute.  Coronary veins filled with air. A thrombus had
formed,  which extended from the  superior vena  cava into  right
auricle, ventricle,  and for a distance of 25  cm. into the inferior
vena cava.   Pulmonary artery  contained  no thrombus, but was
distended with air and spumous blood.   Left ventricle contracted,
contained a small  amount of fluid  blood and air-bubbles.  It was
quite evident that  the thrombus  had primarily formed around  the
catheter, and by new  additions it finally reached the distal portion
of  the inferior vena cava.   Death was produced  by thrombosis.

   Remarks.—The therapeutical  value of catheterization  and
aspiration of the  right auricle for air-embolism is made  appa-
rent by the following tabular arrangement of the experiments:— 
93
			Amount of air		
No. of	Weight of	Amount of air	and blood	Result.	Cause of death.
experiment.	animal.	injected.	removed.		
I	24 pounds.	60 c. cm.	250 c. cm.	Recovery.	
2	30 "	IOO "	120 "	Death	Thrombosis.
3	20 " .	30 "	90 "	Recovery.	
4	40 "	90 "	250 "	Death	Thrombosis.
5	25 "	60 "	SO "	"	Air-embolism.
6	15 "	60 "	60 "	Recovery.	
7	48 " 1	120 "	360 "	Death	Thrombosis.
  From this table it will be seen that of seven animals subjected
to the operation, three  recovered  and four died.  The amount
of air  injected in the subjects of experiments Nos. 1 and 6 was
sufficient  to destroy life, so that we can  safely assume that the
animals would have died, but for the speedy resort to catheteri-
zation and  aspiration.   In  the subject  of experiment  No. 3
recovery might  have taken place  without the operation,  as the
relative quantity of air was much smaller.  In the four fatal cases
death was produced only once from  the presence of air, while
the direct cause of death in the  remaining three was  due to
thrombosis.   All possible precautions were exercised to prevent
the accident.   The  catheter was made  aseptic by  thorough
cleansing  and immersion in  a five per cent, solution of carbolic
acid.   Before the operation the instrument was  kept ready for
use in an alkaline solution of the  temperature of the body, and
yet this accident happened  in three out of seven cases.  It is
now asserted that  the  introduction of aseptic bodies into the
circulation does  not give rise to thrombosis, and  it may be
possible that some of the instruments used, in  spite of the pains
taken to render  them aseptic, were still not  in a  fit condition to
be used for such  a  purpose.   Catheterization  and  aspiration of
the right auricle for air-embolism  compare favorably with punc-
ture and aspiration of the right ventricle as a life-saving pro-
cedure, but  the  former operation is more dangerous on account
of the tendency to the formation of a thrombus within or around
the catheter.  If this formation of thrombus could be avoided
with certainty, catheterization and aspiration of the right  auricle 
94
would recommend itself as  the  most  expedient and  reliable
therapeutic agent  in  cases where  life is threatened  by air-
embolism.

        XVI. Prophylactic  Treatment of Air-Embolism.

   As clinical experience and experimental research have shown
that the admission of air into veins is not an infrequent occur-
rence and often has resulted in death, it is the duty of the sur-
geon in extirpating tumors, which are in close proximity to the
large veins  within  the  area of the  " danger  zone" to resort to
measures which will prevent the ingress of air in case a vein is
accidentally wounded.  The following precautionary means de-
serve consideration:  i. Position.   2. Compression.  3.  Liga-
ture.  4. Aseptic tampon.
   1. Position.—Regular respiratory movements of the chest are
necessary to maintain the equilibrium between  the  arterial and
venous circulation, and should always be secured in  operating
in close proximity to veins  at the base of the neck, as during a
sudden deep inspiration the  direct aspiratory effect of respiration
in the veins extends to  some distance, constituting thus the
direct cause of entrance of air into an open vein.  Before anaes-
thetics were used, Poiseuille advised that the  patient should be
instructed not to make any  deep inspiratory movements during
the operation.   At the present time the same object is better
obtained by keeping the patient  thoroughly  and continuously
under the influence of the anaesthetic.   Gerdy aimed to prevent
the aspiratory effect of  respiration by recommending  compres-
sion of the thorax, but the advice is more useful in theory than
in practice, as suspension of the thoracic movements for any
length of  time would necessarily interfere with respiration and
cause death by asphyxia.
   The venous circulation is  greatly influenced by position.  In
the elevated position the blood gravitates towards the heart and
the veins  are emptied.  If in this  position a vein is wounded,
and the walls of the vessel do not collapse on account of some
anatomical peculiarities, or from rigidity of the vein wall itself 
95
due to pathological changes, a vacuum is formed and air enters.
The entrance of air into a vein distended with blood is a physical
impossibility.   In reading  the clinical  histories of cases where
air entered veins  during operations, we are met  by the fact that
in almost all of the cases, the wounding of the vein was not fol-
lowed by any  considerable loss of blood, and we are usually told
that the air entered almost immediately after the vessel was in-
jured, which would indicate  that the vein was empty or  nearly
so at the time it was wounded.  In a number of cases the  blood-
less condition  of the vein attracted the attention of the operator,
and is particularly emphasized in the description of the cases.
As  long  as the interior of a vein  and the lumen of a wound in
its walls  are occupied by a continuous stream of blood there is
no  danger  that air will be  admitted.   Statistics tend to show
that the  accidental admission of air into veins  was more fre-
quent  before  anaesthetics were  used, a fact which we can only
explain by assuming  that the patients were then usually  placed
in a sitting or semi-recumbent position during the operation,
positions favorable to the return of venous blood  from the cervi-
cal region.  On  the  other  hand, the safe administration of an
anaesthetic necessitates the horizontal position in which the veins
of the neck become  distended  with blood.   In the former in-
stance the  return of venous  blood  in the vessels of the upper
portion of the body was favored by the elevated position, and
the vacuity thus produced  in the veins constituted the most im-
portant and potent factor in determining the entrance of air.  In
the horizontal position, the veins of the neck  are never  empty,
and  to effect  entrance of air the exciting  cause must operate
with  increased intensity.  On this  account  the horizontal or
dependent position of  the  region of the body  to be operated
upon, recommends itself as the simplest prophylactic measure
against the accidental entrance of air into wounded veins.  This
position increases the risk of hemorrhage from the injured vein,
but this accident in its immediate effects is less disastrous to the
patient and more readily under the control of the surgeon than
air-embolism.
  2. Compression.—Compression of  a vein  between the  seat of 
96
operation and the heart for the purpose of guarding against the
entrance of air may be divided  into  intermediate  and direct.
Intermediate compression is only applicable in cases where the
external jugular vein is in danger of  being wounded.  If the
tumor to be extirpated is not located too low in the region of the
neck uninterrupted  digital  compression of the external jugular
vein just above the  clavicle can be relied upon in preventing
entrance of air through this vessel.  The internal jugular and
axillary veins are so  deeply situated that intermediate digital
compression cannot be relied upon in the prevention of air-
embolism, consequently it becomes necessary  to resort to direct
compression whenever it becomes necessary to guard against
this accident.   Warren recommended  that in the extirpation of
tumors  which are in close proximity  to the large veins of the
neck and axilla, the separation of the pedicle should be reserved
until  the last in order to enable the operator to compress the
vein between the seat of operation and the heart more effectually,
should the vessel be injured during the operation.
  Langenbeck advised that the vein on the distal and proximal
sides of the tumor should be exposed  to sight as a preliminary
measure before attempting the removal of the tumor with  a
view to  facilitate direct compression in  case the vessel should be
opened  during the dissection.   The adoption  of either of these
precautions would successfully prevent a second ingress of air,
but would not protect the patient against  the dangers arising
from the first dose.   Permanent central  compression augments
the danger of wounding  the  vein from the turgidity of the
vessel which  it produces,  while  distal compression would  be
attended by the same risk, only in an opposite way, by rendering
the vessel empty and consequently more difficult of recognition.
If the attachments of the tumor to the  vein are of such a nature
that they can be separated without great danger of injuring the
vessel, then the vein  should be isolated on the  proximal side
and the vessel compressed with a haemostatic forceps which will
afford greater safety than digital compression,  at the same time
the field  of operation  is not  obscured  and  narrowed  by the 
97
 fingers and hand of the assistant, an item of great importance in
 operating in the regions of the neck or axillary space.
   Injury  of  the  vein  in  such   instances will be promptly
 announced  by  hemorrhage  from  the distal  portion, but the
 entrance of air into  the right ventricle  is  made  impossible
 by the prophylactic compression of the vessel between the seat
 of operation and the heart.  Should the vein be wounded, any
 further ill effects arising from this accident can be prevented by
 applying a  lateral ligature or tying both ends of the vein accord-
 ing to the size of  the wound, before removing the compressing
 forceps.   In all operations where any of  the  large veins are in
 danger of being wounded the position of the parts should be
 such as to retain as nearly as possible their normal anatomical
 relations.   The operator should make haste slowly, and identify
 every  structure before using cutting instruments.  In extirpating
 tumors that  are  deeply  situated,  the  external  incision  should
 always be large so as to afford free access to the base or deepest
 portion of  the growth  to  be  removed.  A  pair of Billroth's
 retractors will do  good service during the deep dissection.
   Hemorrhage must be carefully arrested as it occurs, in order
 to enable the surgeon to see  what he is doing.  Isolation of the
 vein from the tumor  must be accomplished by the use of blunt
 instruments,  and  all  firmer  attachments  should be  carefully
 examined and identified before using the knife or scissors.  As
 it is usually impossible, or, at any rate, impracticable to find the
 vein in the  tumor or its  immediate vicinity,  the  rule  should
 always be followed to expose the vessel  for some distance from
 the tumor on the proximate side, and then follow it by carefully
 separating the attached  tissues  by means of blunt instruments.
 Under antiseptic precautions the jugular vein  can be isolated for
 a great distance without fear of  compromising the vitality of its
 tissues or causing thrombosis.  When a tumor is  attached to
 the jugular vein it is a dangerous practice to make traction on
the tumor for the  purpose of facilitating  the deep dissection, as
this procedure will disturb the normal anatomical relations of the
vessel  and  thus expose it  to  greater risk of  being wounded.
Free access to the base of the tumor  must be secured without
       7 
98
displacing  the subjacent vein.   As soon  as the  tumor  has
been  isolated from  the surrounding  tissues a  thorough  ex-
amination  should be made of the  extent  of its  base and  its
relations to the subjacent vein before proceeding  any further
with the dissection.  If the conclusion  is reached that the vein
is so intimately connected with the base of  the tumor that it is
in great danger of being injured during the further progress of
the extirpation, it becomes necessary to resort to direct com-
pression of the distal and  proximal portion of the  vein.   By
isolating and  compressing the vein on each side of the tumor
both excessive turgidity and emptiness of the intervening por-
tion of the vein are avoided.   The amount of blood  in  the vein
between the two points of compression can be regulated, and
only a sufficient quantity is allowed to remain  to indicate the
exact location of  the vessel.  Compression  is again  made with
haemostatic forceps.   After the complete removal of the tumor
the forceps on the  distal  side of the vein  is removed first, in
order to test  the integrity of the vessel and wTith a view to pre-
vent any possibility of the entrance of air.   If no hemorrhage
takes place we may be satisfied that  the  vein  has  not been
injured, and the remaining pair of forceps can be safely removed.
In such cases the exposed portion of the vein should always be
covered with the adjacent  tissues by deep  sutures en etages of
catgut before closing the wound.  If the vein has been wounded
a  lateral ligature is  applied,  or  both ends are ligated  after
complete division of the vessel  before  the  forceps between the
vein wound and the heart is removed.   By following this plan
we accomplish the following objects:  I.  Hemorrhage from
the  injured vein is slight and perfectly under  the control of
the surgeon.   2.  Absolute  security against the  entrance of air.
3. A more thorough removal of the tumor.
   3. Ligature.—In all cases where a large  vein passes through
the substance  of the  tumor  and where isolation of the vessel
appears inexpedient or impossible,  double ligation recommends
itself as the safest prophylactic measure both against hemorrhage
and air-embolism.   As soon as the base of the tumor is reached
the vein is exposed  on each side and tied with  catgut, and  the 
99
intervening portion is extirpated with  the tumor.   By adopting
this plan we secure for  the patient absolute protection  against
hemorrhage and air-embolism.  Adequate collateral  circulation
is established in a short time, so that  ligation or excision of the
internal jugular or axillary veins  can be done under antiseptic
precautions without danger of causing serious disturbance  of
the cerebral circulation  in the former, or gangrene of the arm in
the latter  instance.   Isolation and  ligation of the vein on the
proximal side of the tumor should always be resorted to,  when
injury to the vein  is unavoidable.    In  case  the  prophylactic
ligation of the vein  on  the distal side of the tumor is rendered
difficult or impossible  by existing circumstances, the following
course can be pursued.   After ligation of the vein on the proxi-
mal side  of the tumor a haemostatic forceps is applied a little
distance from the ligature on the side of the tumor, and the
vessel is divided between  the forceps and the ligature.   The
ligature prevents the entrance  of air, and the forceps serves the
purpose of a temporary haemostatic agent during the extirpation
of the tumor.  The  base of the tumor with the vein is detached
when the vessel on the  distal side of the tumor is sought for and
tied, and the remaining attachments of the tumor, including the
vein,  are cut.   This  plan affords protection against the entrance
of air, but  during the separation of the tumor  hemorrhage may
occur from accidental wounds of the distal portion of the vein,
which, however, can be readily controlled by compression with
haemostatic forceps  until the vessel is permanently secured on
the distal side of the tumor.
  4. Aseptic Tampon.—If a large vein has been wounded which
from  its location is inaccessible to the ligature, permanent com-
pression with a graduated aseptic tampon will arrest the hemor-
rhage and  prevent further ingress of air.

         XVII. Operative Treatment of Air-Embolism.

  Considering  the  infrequency of  air-embolism as compared
with the number of vein wounds, it is not surprising to find that,
as a rule, surgical writers have little, if anything, to say on the 
100
subject  of the  prevention  and treatment of air-embolism.  It
must  be apparent to all, that  in following  the rules laid down
when we considered  the prophylactic  treatment, the accidental
introduction of air into veins is prevented  almost to a certainty,
and at the same time they will also furnish a safe guide in the pre-
vention and management of venous hemorrhage when operating
within the area of the " danger zone."   If the preventive treat-
ment  is carefully carried out, air-embolism will become  one of
the rarest accidents in surgery.  As even  with the greatest care
an accident of this kind might  happen, it  becomes necessary to
allude to the operative treatment of air-embolism.  The occur-
rence of the  accident is sometimes announced  by an audible
hissing or sucking sound, and is always followed almost instantly
by  a  well-marked train of distressing  symptoms  which  are
directly referable to a mechanical obstruction  to  the circulation
in the right side of the heart  and  the  pulmonary artery.  The
treatment must depend on the quantity of air which has entered,
and the  severity of the  symptoms produced  by it.  The the-
rapeutic   measures  should be aimed  towards  meeting  the
following indications:  I.  Prevention of further  ingress of air.
2. Administration of cardiac  stimulants to sustain  the action
of the heart.   3. Venesection  to  relieve  intravenous  pressure.
4. Aspiration of air from the right  side of the heart to prevent
over-distension and paralysis of right ventricle.
  1. When air has entered through a gaping wound  in a vein
during inspiration there is  great danger that the same occur-
rence will repeat itself during  successive respiratory movements
of the chest, hence the first object  of treatment consists in clos-
ing the wound  in the vein.  This is most quickly done by digital
compression, which is continued until the vein has been rendered
impermeable by ligature  or  permanent  compression.  If the
symptoms are urgent no time should be lost in securing the
vessel until the patient has rallied  from the  immediate effects of
the air-embolism.  It is also necessary to  postpone the  perma-
nent closure of the vein until the time has elapsed for any indi-
cations  to arise which would  call  for venesection or  operative
removal  of the air from the right side of the  heart, as in such 
101
cases it may become necessary to utilize the wounded vein as a
route for the introduction of a catheter into the heart.   When
the time has arrived  for closing the vein the finger should not
be removed suddenly from the vessel for fear of causing a repe-
tition of the accident;  it should remain in situ until the vessel
can  be compressed on  the proximal side of the vein wound by
an  assistant.  The exact location  of the wound  will now be
probably indicated by escape of blood from the distal end of the
vein when the vessel can be seized with a forceps, and after its
isolation, a double ligature is applied.   If it  is found impossible
to ligate the vein, then the vessel  is compressed  in the wound
by means of  a graduated aseptic  tampon retained in place by
uninterrupted  pressure until definitive closure of the wound has
taken place.
  2. The heart's action must be supported  by position and by
the use of cardiac stimulants, which are best administered sub-
cutaneously and by inhalation.  The patient must be placed in
the  horizontal position with a  view of guarding as  much as
possible against the occurrence of cerebral anaemia as well as to
lessen the intravascular pressure to a minimum.  If the quantity
of air admitted is not sufficient to produce instant  death by
paralysis of the right side of the heart in the  diastole, the  symp-
toms which follow always point towards an embarrassment 01
the circulation in the right side  of  the heart  and the pulmonary
artery, which  are  always accompanied by dyspnoea, combined
with evidences indicating the existence of acute cerebral  ischae-
mia.   If death does  not take place within  a few minutes from
obstruction to the circulation through the pulmonary artery by
the presence  of air  in  that vessel, then the  contractions  of the
right ventricle will force at  least a part of the air through the
pulmonary capillaries into the general circulation, thus prevent-
ing death by  asphyxia.  As soon as the air-embolism  of the
pulmonary artery has been  relieved the most urgent symptoms
subside, as the air-emboli in  the  arterial system are distributed
over a  larger  area and consequently produce an  embolism of
lesser  extent  and gravity  in more distant and  less essential
oro-ans.  The  safety of  the  patient  depends  on the capacity of 
102
the right ventricle to force the air through the pulmonary into
the general circulation, in  other words, upon the time which is
required in removing the emboli from the pulmonary artery into
the systemic circulation.
   Nitrite of amyl, from its stimulating properties upon the heart
and from the rapidity  of its action, would recommend itself in
the form of inhalation as the most efficient drug in preventing
threatened syncope.   The  temporary dilatation  of the  small
bloodvessels  would tend to produce, at least for a short time, a
diminution of the intravascular  pressure.   Hypodermatic injec-
tions of camphor and  alcohol,  although  slower in their action,
would also assist in antagonizing the deleterious effect of over-
distension of the right ventricle by the air-embolus.  In  all of
my  experiments where electricity was used  it had no  effect
whatever upon  the heart,  even when applied directly  to  the
organ, hence it would  be of no use to resort to this agent for
the  purpose of sustaining  or  re-establishing the movements of
this organ in serious cases of air-embolism.
   3.  In all post-mortem examinations after sudden  death from
air-embolism two constant  pathological  conditions are always
found present:  1.  A comparatively empty state in the left side
of the heart and throughout the entire arterial system.   2. Dis-
tension of the  right ventricle and intense  engorgement of the
whole venous system.   Both of these conditions are, of course,
due to  the presence of air in the ultimate branches of the pul-
monary artery, which  prevents the free transit of the venous
blood through the pulmonary capillaries into the left side of the
heart.  As a direct result of these conditions, we have a diminu-
tion of the  intravascular pressure in the left side of the heart
and arteries, and  a  corresponding increase in the right  side of
the  heart and the veins.  The  immediate and  greatest danger
arises from an accumulation of air and blood in the right side of
the heart to  such  an extent as will arrest the ventricular con-
tractions by  over-distension before the equilibrium between the
arterial and venous circulation  can be restored by the removal
of the air-emboli  from the pulmonary artery into the  general
circulation.   Even the most  extreme antagonists to the lancet 
103
 must  acknowledge the benefit  which follows its use in similar
 conditions of the circulation caused by other pathological con-
 ditions.  In severe cases of pneumonia  where the  circulation
 has been so much obstructed that death is threatened by venous
 engorgement and over-distension of the right ventricle, the free
 use of the lancet is the safest and most efficient means in equal-
 izing the circulation, as by the abstraction of blood from  one of
 the veins,  the  intravascular pressure in the  veins  and right
 side  of the heart is diminished in the  promptest  and most
 direct  manner.   As  the adventitious  air  in the  pulmonary
 capillaries can and will be  forced into  the general  circulation
 by the  contractions of the  right ventricle, and  as  the urgent
 symptoms will subside after this has taken place, it  is of para-
 mount importance to gain time by protecting the right ventricle
 against an undue amount of additional labor.  Among  the  in-
 direct remedies to accomplish this object venesection deserves
 the first place.   I could refer to a number of  the experiments
 where copious bleeding from the distal portion  of the open vein
 was promptly followed by  improvement  in all the  symptoms.
 Vulpian asserted that, after insufflation of air into veins, the con-
 tractions of the heart were restored after the organ had ceased
 pulsating, by the  abstraction of  blood from the  sinuses of the
 brain and the veins of the neck.   I have never  succeeded in  re-
 storing the action of the  heart, after its pulsations had ceased
 completely, by any kind of treatment; but, when the contrac-
 tions have  become  imperfect  from  this cause,  I  know that
 removal of  the  cause of over-distension will restore the force
 and efficiency of the  contractions.   H.  Fischer1 sarcastically
 alludes to this  valuable agent  in the treatment  of  air-embo-
 lism as  are medy from which only homoeopaths  would expect
 to  derive any  benefit.   An expression  of this kind concern-
 ing such a valuable remedy, and in  this  particular connection,
 must be looked  upon  as  unscientific  and contrary to well-
established  clinical and pathological  facts.  I  must,  therefore,
insist that venesection from the distal end of the wounded vein
will prove beneficial in all cases  of air-embolism where venous

         i Ueber die Gefahren des Lufteintritts in die  Venen, p. 17. 
104
 engorgement and over-distension of the right ventricle constitute
 elements of imminent danger.  If practicable, the bleeding should
 always be done from the distal end of the wounded vein while
 the proximal end is compressed or ligated.  The advantages of
 doing so are  obvious for the following reasons :   a.  The abstrac-
 tion of blood is accomplished in the  shortest possible space of
 time.   b. The blood escapes in a large stream from a capacious
 vessel,   c. No  additional instruments are required, and the in-
 fliction of another wound is obviated.
   4.  Clinical experience and experimental research teach us
 that when a  certain amount of air enters the right side of the
 heart, death invariably takes place in a very short time and cannot
 be prevented by any of the indirect  methods of treatment.  It
 seems to me that in such cases  it would be legitimate  and
 proper  for the  surgeon to resort to some procedure by which
 the air could be removed directly  from  the heart.   To accom-
 plish this object Fischer recommends that forcible expiratory
 movements should  be excited by inducing coughing, sneezing,
 or vomiting, with a view that during the forcible  compression
 of the thorax the aspirated air would be forced  out  through the
 wound in the vein.  Against this advice the following objections
 may be entered:  1.  The difficulty or impossibility of exciting
 coughing, sneezing, vomiting, or any other act on part of the
 patient  when in a condition of collapse.   2. If during the forci-
 ble compression of the chest, the air is forced backwards, it will
 be just as likely to pass into other veins  than the one through
 which it entered.  3. The difficulty of preventing the admission
 of more air during the forcible inspiration following the forcible
 expiration.  4.  During prolonged forcible expiration the  intra-
 vascular pressure in the veins and right side of the heart is greatly
 increased, thus  constituting an additional source of immediate
danger.   5.  Forcible  expiratory movements of  the thorax, by
compressing the heart, will be more likely to force the air onward
with the venous current into the pulmonary artery where it will
do the most harm by causing asphyxia from a sudden and exten-
sive air-embolism in that vessel.
  The only direct means of  removing air from the heart consist 
i<>5
 in  puncture of the right ventricle and  catheterization of the
 right auricle combined with aspiration.   The experiments made
 by myself in this direction have demonstrated that  puncture of
 the right ventricle with  an aseptic-needle two  millimetres in
 diameter is  in itself a harmless procedure.  When we remem-
 ber that in the human subject the heart has often been the seat
 of  more extensive  injury without any  immediate or remote ill
 effects, we must abandon the idea that  slight injuries of  this
 organ are necessarily fatal.  Small aseptic wounds of the heart
 heal  rapidly, and in the same manner  as in any other organ of
 the body.  The hearts which I  show  you were removed from
 dogs a few  days to  three weeks after  puncture; and not in  a
 single specimen are we able to detect any evidences of organic
 changes, either  in the  substance  of  the organ  or its serous
 membranes.  In most of the specimens  the  point of puncture
 is marked by a minute cicatrix, visible upon  the surface of the
 visceral pericardium.    In  penetrating wounds  of the heart
 hemorrhage into the  pericardium  and compression of the heart
 from this cause are to be feared, and constitute the  only source
 of  immediate danger.   There is no plausible reason why in the
 human subject an oblique puncture of the right ventricle should
 be  followed  by more hemorrhage  than in animals, and conse-
 quently I have no hesitation  in  recommending puncture  and
 aspiration of the heart as a justifiable procedure  in cases of air-
 embolism which would otherwise  necessarily prove  fatal.  The
 question naturally arises : What symptoms indicate a resort to
 puncture and aspiration of the right ventricle?  Two different
 conditions, as far as  time and symptoms are concerned,  may
 call for this operation.  The puncture  should  be made as soon
 as  possible after the entrance of  air, in the event that  the
 primary effect of the heart embolus has produced sudden over-
 distension and paralysis  of the right  ventricle,  an  occurrence
 which would be indicated  by immediate collapse and partial or
 complete suspension of the heart's action.  In such a case  the
 direct  withdrawal of air  from the  right ventricle,  as  soon as
possible after its entrance,  affords  the only  possible  hope of
restoring  the pulsations of the heart by removing the cause of 
io6
the mechanical over-distension.  In the second class of cases
the patient has  collapsed,  but the  heart  has  withstood  the
primary effect of  the aspirated air.  The heart's  action is rapid
and tumultuous, perhaps at times intermittent.  The ear applied
over the cardiac region detects distinct churning sounds.  Respi-
rations are  rapid, and  all symptoms  point towards imperfect
circulation and aeration of the blood as expressed by the pallid
face and  blue  lips.   Some of the air has  passed from the right
side  of the heart  into  the  pulmonary artery,  and from  the
obstruction of the circulation through this vessel the right ven-
tricle becomes more and more distended, the contractions there-
fore are less perfect and more frequent.  At this stage of things
puncture and aspiration of the right ventricle will overcome the
most  urgent symptoms by  the  removal of air and  spumous
blood, and enough  time may be gained for the  right ventricle
to force the remaining  air-emboli through the pulmonary capil-
laries into the general circulation, and  the life of the patient  is
saved.   These  are  the  cases where puncture and  aspiration  of
the right ventricle can be done with a fair prospect of not only
relieving  urgent  symptoms, but of ultimate recovery.   They
are also more favorable from the fact that more time is  afforded
the surgeon in procuring and using the aspirator.  The punc-
ture should always  be made in an oblique direction, from below
upwards, so as to  make a  valvular tract in the heart for the
purpose of  preventing  hemorrhage into  the pericardium,  and
also for giving the point of the needle a direction in which  it is
least likely to injure the opposite endocardial lining.  The left
intercostal space, between the fourth and  fifth  ribs, about an
inch and  one-half from  the margin of  the  sternum, is  selected
as the best point for  making  the  puncture.    The  needle,
thoroughly disinfected, is connected with the aspirator, and,  as
soon as its point  is  buried in the tissues, a vacuum  is created  in
the aspirator, and the needle is advanced  slowly until spumous
blood is  felt and seen to escape, when  it is firmly held in  this
position, and  the contents of the  ventricle are withdrawn  as
quickly as possible.  My experiments  have satisfied me  that I
generally removed the needle too soon, not  having  withdrawn a 
io7
 sufficient quantity of blood and air.  In some of the experiments
 I followed  the  aspiration by blood-letting with marked benefit.
 Removal of the same quantity of blood directly from the right
 ventricle would have been productive of more good, as less air
 would have been left in the heart.   The experiments on dogs
 have shown that these animals will always recover if the quantity
 of air injected  into the veins does not exceed one c. cm. of air
 to each  pound  of  its weight.   Double this  quantity  must be
 considered  a fatal dose.   If, therefore, we can  remove by aspira-
 tion  only a portion of air directly from  the  right ventricle we
 may be able to  maintain the  action of the heart and respiration
 until the embolism of the pulmonary artery has been relieved
 by the passage  of air from this vessel into the general circula-
 tion.  When the presence of  a foreign body  in any other part
 of the body threatens to destroy life no surgeon would hesitate
 to make  an attempt to remove it, even if the effort should be
 attended  by an  increase of the immediate risk. Air in the right
 side of the  heart acts the part of a foreign body, and, when it
 destroys  life, it  does so by causing mechanical  obstruction to
 the  circulation.   The timely  removal of the air  is  the only
 rational  treatment  in  all cases  where simpler measures  have
 proved inadequate  in preventing a fatal  termination.  An aspi-
 rator in  good  condition should be  on hand in  every  well-
 regulated hospital,  and of ready  access in cases  of  emergency.
 If air-embolism occurs  during  an  operation  the  instrument
 should be  used before  the  heart has ceased pulsating, when
 prompt action on part of the  operator may obviate  death in an
 otherwise hopeless case.  The experiments on catheterization of
 the heart were undertaken with a view to simplify the  operative
 removal  of  air from the right side  of the  heart.   An aseptic
 catheter was introduced  into the wounded vein and passed into
 the right auricle, and by aspiration air and spumous blood were
 removed.  The  result showed that  some of  the animals  were
 saved from  impending death  by this simple procedure.  The
 great danger attending this operation  consisted in the tendency
 of the blood to coagulate within or around the distal end of the
catheter,  and  death from the  formation of a thrombus in the 
io8
large veins and right side of the heart.  If the formation of a
thrombus could  in  some way be  prevented with  certainty,
catheterization and aspiration  of the heart would recommend
itself as  the simplest and safest measure in the operative treat-
ment of  air-embolism.
   Catheterization of the heart  is not a new suggestion, as the
introduction of a tube into the heart for the same purpose was
recommended more than fifty years ago by Magendie.  I should
recommend the adoption of  this procedure only in case when
the air has  entered  through a wound  in  the  internal  jugular,
and when the symptoms leave no doubt that death would  be
inevitable without direct removal of the air by aspiration.  An
aseptic Nelaton's catheter with an open  end should be intro-
duced into  the wound, through which the  air  entered, and
pushed as quickly as possible as  far as the auricle, when the
air and spumous blood can be withdrawn  by the mouth  in the
absence of any other means of aspiration.   Admission of more
air is prevented by compression of the distal end of the instru-
ment before and between the aspirations.   The whole operation
must be done as quickly as possible for the purpose of prevent-
ing coagulation of the blood.  For the same  reason an instru-
ment of large  calibre should  be used.
   In  presenting to you the  practical  outcome of my  experi-
mental wrork in the  form of these few suggestions on the opera-
tive treatment  of air-embolism, I am fully  aware  that  in  your
own  minds you have decided  that my labor has  been in vain,
and that the means suggested do not  admit  of application in
practice.   In reply,  I  will say that desperate cases  call for
desperate measures.   When  death stares us in the face we have
not only  a right, but it  becomes our most imperative  duty to
resort to any  plan of treatment which  holds  out the slightest
hope  of saving the  life of the patient.   For myself I am fully
convinced of the safety and usefulness of puncture and aspiration
of the right ventricle  in grave cases of air-embolism,  where
simpler means have proved of no avail.  When no  aspirator is
within reach I also  believe  in the propriety of catheterization
and aspiration of the heart as  a last resort in all  cases of air- 
109
 embolism where death would surely take place without it.   If
 by the adoption of either of these methods of direct treatment
 of air-embolism a single human life should be saved, I shall feel
 amply rewarded for the labor incurred in the preparation of this
 paper.
   In conclusion, I beg leave to submit the following resume for
 your further deliberation and discussion:—
   I.  The presence of adventitious  air in the vascular  system
 during life gives rise to air-embolism.
   2.  Each air-embolus constitutes a mechanical source  of partial
 or complete obstruction  to the  flow of  blood in  the  vessel in
 which it is located.
   3.  Aspiration during the inspiratory movements of  the chest
 is the direct or  exciting cause of ingress of air into a  wounded
 vein or sinus.
   4.  Elevation  of the head is the  sole predisposing cause of the
 entrance of air in wounds of the superior longitudinal sinus.
   5.  In veins the predisposing causes consist in—
       a. Elevation of the part wounded.
       b.  Pathological or anatomical conditions which prevent
            collapse of the vein when  it is wounded.
   6.  Insufflation of a fatal quantity of air into a vein  produces
 death by—
       a.  Mechanical over-distension of  the right ventricle oi
            the  heart, and paralysis in the diastole.
       b.  Asphyxia from obstruction to  the pulmonary  circu-
            lation consequent upon embolism of the pulmonary
            artery.
   7. Insufflation of the same quantity of air into arteries is less
dangerous than when  introduced into veins.  When  death is
produced  in this manner it results from—
       a.  Acute cerebral ischaemia.
       b.  Secondary venous air-embolism.
       c.  Intense collateral engorgement  of the vessels of the
            brain and spinal cord.  The manner of death being 
no
           determined by the amount of air injected, and  the
           direction in which the injection  is thrown, as well as
           the time which has elapsed  between the operation
           and the fatal termination.
  8. Air  injected into  arteries is  readily  forced  through  the
systemic capillaries into the venous  circulation and right side of
the heart by the powerful contractions of the left ventricle.
  9. Air-embolism of the pulmonary artery is relieved in a com-
paratively  short  time, provided the contractions of the  right
ventricle continue unimpaired  for a sufficient length of time to
force the air through the pulmonary  capillaries into the general
circulation.
  10. The prophylactic treatment consists in proximal or double
compression, or ligation of the vein which is endangered by the
operation.
  11. The indirect treatment has for its objects—
         a. Prevention of admission of air.
         b. Administration  by   inhalation  of  hypodermatic
             injection of cardiac stimulants.
         c. Venesection.
  12. The direct or operative treatment by—
         a. Puncture and aspiration of the right ventricle.
         b. Catheterization and aspiration of right auricle, which
             are  proposed with a  view to obviate the direct
             cause of death by the removal of air and spumous
             blood, thus  relieving  directly the over-distension
             of the right ventricle, and, at the same time, to
             guard against a  fatal embolism of the pulmonary
             artery.
  13. The results obtained by experiments on  animals warrant
the adoption of  the operative treatment  of air-embolism  in
practice, as a  last resort, in all cases  where the  indirect treat-
ment has proved  inadequate to meet the urgent indications. 
Ill
                        DISCUSSION.

Dr. J.  Collins Warren, of Boston, Massachusetts.
  I do not know that it is  necessary to say anything in  regard  to
the admiration which we all feel for the arduous labor of  Dr. Senn.
The work is of a character that we should value and cherish.  We
have too little of this  kind  of  work in this country, and should  be
glad to see more of it.
  In regard to the lesion of which  he treats, I think that the criti-
cism may be made that it is rather obstetrical than surgical.  There
are few members of  this Association who have met  with such  an
accident that has called for any exercise of their surgical skill.   A
certain amount  of aspiration of air into veins has been seen by most
every  surgeon,  but  alarming  symptoms  are  of rare occurrence.
The cases are not numerous in surgical literature.
  According to the investigation  of those who have studied this
subject beside  Dr.  Senn, it appears that the lesion amounts to a
blowing  up of  the right side of the  heart, so that  its  action is
paralyzed and it cannot contract.   Various other theories as to the
cause of death  have been brought forward, such as anaemia of  the
brain and air-embolism of the lung, but it seems  to me that  the
lesion  described is  sufficient  to explain  the result.   The  heart
undertakes to force out of  it  that which  it cannot  squeeze or com-
press, and it is paralyzed in  its  efforts to do it.  It has been compared
by  some  to  fat-embolism.    We  know  that  fat-embolism, which
sometimes follows surgical injuries, may  be present  and not  pro-
duce any symptoms.  The capillaries of the lung may be filled with
fat-emboli and yet no symptoms be produced. At  autopsies a large
amount of such deposits are sometimes found without their existence
having been  suspected during life.  One  lung may be completely
obstructed by disease, and  yet the patient be in a condition to live,
as far as  the lung itself is concerned.   It does not seem probable
that the presence of air in the lung is necessarily fatal.   It is  the
heart and the large vessels which bring the blood  to the heart that
are blocked,  and circulation in them is stopped.
  Experiment has also shown that a large quantity of air can  be
injected  into the circulation if it  is done slowly.    We  have then 
112
 frothing of the blood, but no mechanical obstruction to the heart,
 without embolism in the lung and arterial circulation, and without
 any  important  or dangerous symptoms  resulting  therefrom.   Dr.
 Senn could tell us how large quantities can be injected in the horse
 without producing bad effects.
   I presume that this condition occurs in  a large number of surgical
 cases.  I remember performing tracheotomy  on  an adult female,
 in which the superficial veins were opened.  I  could hear the click-
 ing  of  the air in the wound with each inspiration.   I paid no atten-
 tion  to it,  and  no bad symptoms resulted.  I presume that it  can
 only be of serious  import when  some  large sinus  like the  internal
 jugular vein  has been largely opened, or if the longitudinal sinus
 or the  axillary  veins have been opened, and a large quantity of air
 has  been sucked in by a sudden inspiration.
   In speaking of the axilla, I may say that I have noticed aspiration
 of air into the axilla, which for the time  being disturbed me, as it
 simulated  somewhat this trouble.   In  the pumping efforts of  the
 thorax, air may be  drawn into the loose connective  tissue of  the
 axilla, producing a  sound resembling that of the  entrance of air
 into the vein.
   Dr. Senn stated that this accident was more common  in  surgery
 before the  days of anaesthesia than since.   He ascribed that to  the
 erect position  favoring the entrance of air.  It occurred to me that
 there might be another way of explaining the fact, if such it  be, and
 that  is,  that the tension  which was  placed on the  muscles of  the
 patient  under any  painful  operation  and  the gasping  efforts at
 particularly painful  periods, might impel  the  individual to take a
 sudden, short, sharp inspiration with all the muscles pulling  in such
 a way as to open the veins and draw in several large bubbles of air.
 I should think some such explanation as that  quite as possible as
 mere posture.
  As I  have said, it is  in obstetrical practice that we meet with this
 accident in all  its hideousness.  In preparing for this discussion, I
 was reading over an  interesting report on this subject by one of our
 medical examiners,  Dr.   F.  W.  Draper.   Several cases of  air-
 embolism following attempts to produce abortion have occurred in
Boston.   One  was that of a woman  several months advanced in
pregnancy who went to an abortionist.  She sat on a bed while he
introduced  an  instrument into the uterus, and then passed a syringe 
H3
 and began to pump in air, it is supposed.  Air was forced in at any
 rate.  In about fifteen minutes,  she  gave a low moan, gasped once
 or twice, and in half a minute was dead.  At the autopsy, the right
 side of the heart was distended  with  air.  The ascending cava was
 also filled with air.  Air was  found  not  only in these positions, but
 also in the capillaries of the lung and of the arterial system, so that
 when  the sternum was cut through, air  bubbled out from the arte-
 rioles of the anterior mediastinum.  It was argued in that case, that,
 as the air had gone so far, it  might  have been possible that it had
 been introduced with  a vaginal douche previous to coming to the
 abortionist's office.  That was disposed  of by the statement  that the
 circulation makes its round in a few seconds, and air can be rapidly
 distributed in a short space of time.  As  Dr.  Senn has mentioned,
 we have  in such  cases, conditions most favorable to the introduc-
 tion of air  into the circulation.   A small amount of air gets into a
 uterus which  is relaxing and  contracting,  there is a certain  amount
 of  hemorrhage with clots which may  cork up the  mouth of the
 uterus and prevent the escape of the air.   Under such circumstances
 there would be  a large number  of holes, communicating with veins
 which have no  valves, and affording a ready egress of air from the
 uterine cavity.  In addition, we have the action of the thorax which
 tends to aspirate the air into the circulation.   Therefore  I  say that
 this  accident is  more likely to occur in  obstetrical than in  surgical
 practice.                                           *
  In regard to treatment, it seems  to me that such a paper as Dr.
 Senn's  is valuable in showing us the mechanical mode of develop-
 ment of  such condition, and in  showing us  the conditions most
 favorable for  its occurrence,  and  consequently telling us more how
 to prevent the accident than to help the patient  after it has occurred.
 As one writer has said, the only  function of the physician  in such
 a case  is  to be  present at the autopsy and confirm the diagnosis.
 That appears to be his sole duty.
  Theoretically, aspiration of the heart  seems  to  be indicated, but
 practically there  probably  never would  be  such a consensus  of
 circumstances which would  enable us to be on hand, to  have the
necessary instruments, and be  quick  enough  in  our  diagnosis  to
enable us to use the  instrument  instantly.  Such an accident is like
a stroke of lightning.  The patient  is dead the moment the condi-
tion  is  recognized.  The  heart  has  been aspirated in other condi-
       8 
U4
 tions, and I suppose it could  be in this.   I do not see that there is
 much ground for comfort in  this reflection, but in this,  as in many
 other conditions, we should hope by a more perfect knowledge  to
 avoid them, rather than to cure them.

 Dr. Edward M. Moore, of Rochester, New York.
   Mr. President, I should like  to introduce to the Association, Dr.
 Gordon, of Portland, Maine, who  will detail to us an extremely
 interesting case bearing  on this  subject.

 Dr. Gordon, of Portland, Maine.
   The allusion of Dr. Warren to Dr.  Draper's case reminds me of
 an  accident which  occurred  to  me during the  past winter, and
 inasmuch as we  profit as much by our faults as by our virtues,  it
 may be interesting to describe it.
   In the hospital to which I am attached, the Maine General Hos-
 pital, I found, when  I  went  on duty,  a  lady with'pelvic abscess.
 Others  had operated by aspiration, but had not found pus.   A few
 days later, the development  having gone  on  rapidlj, I found no
 difficulty in drawing off a pint of  ordinary pus.   A week  or ten
 days later, I did the same thing.  In the  mean time our  house-
 surgeon had been changed, and a new one came on duty.  I would
 say also that the aspirator used in the hospital was a bottle aspirator.
 Those who  are  familiar with it  know that the pump will either
 condense or exhaust the air  in  the bottle, according as  the tube is
 applied to one or the other nozzle.   The new house-surgeon, who
 was not familiar with the instrument, attached the tube at the wrong
 end.  I was attending to the needle, and entered it at exactly the
 same  point as in the previous  operations.   When I was  ready, I
 said, "turn on."   He did so, and at  the same instant the woman
 gave a scream, put her  hand over her  heart, and in half a minute
 was dead.  The  fact was that the bottle had been charged with air,
 the aspirating needle was introduced, I simply made the connection
 between the needle and  the bottle, and the result followed.
  Exactly what happened it is impossible  to say.   This  cavity had
 been exhausted  largely by the previous tappings, and the air may
 have entered through some  of the vessels  in the wall, or  the needle
 may have been passed into a vein.  The air certainly got in.  This
is one of those cases in which there  is nothing  to be done.   I have 
n5
only this to say, that I shall never use such an instrument where it is
possible for any one beside myself to have anything to do with it.

Dr. J. Ewing Mears, of Philadelphia, Pennsylvania.
  Was an autopsy made ?

  Dr. Gordon.   There was not.  The husband objected decidedly
to a post-mortem examination.   I think that there can be no doubt
that death was due to  air-embolism.  The symptoms  were  those
which belong to that condition.

Dr. Charles B. Nancrede, of Philadelphia, Pennsylvania.
  I rise with  mingled feelings of admiration and regret to discuss
this paper.    The  admiration  is for the  indefatigable energy of
our Fellow,  Dr.  Senn, and  the regret is  that  I have  nothing
especially new to offer  on this very important, and I think rather
neglected, subject.  It is true, as he stated in his historical account,
that it had  been long known to physiologists that  injection of air
into a vein in sufficient quantity was fatal.  The original idea was
that a single bubble was  fatal.   The first recorded case is usually
stated to be that of Beauchesne in 1818.  It is said that the elder
Larrey had  frequently observed it on,the battle-field from ball or
sabre wounds, I cannot  say which, but more  likely  the  former.
My authority for the  statement  is a systematic work on surgery, in
which it is  stated that Larrey said to Brodie, when looking at the
picture of a man with a  wound  in  the  neck:  "Ah!  I know how
that man died.  I have frequently seen them die from aspiration of
air into the veins on the battle-field." If my authority is reliable,
Larrey antedates Beauchesne in  his  observations,  although Beau-
chesne was the first to record this accident.
  I think that it should  always  be  borne in mind in  performing
experiments  that animals are not human beings.   I  am free  from
any prejudice against experiments, for my graduating thesis was an
experimental one, and I had the honor at the meeting in Cincinnati
of laying  before  the Association  the  results of my experiments on
inflammation in animals.  As Dr. Senn  mentions, death occurs in
some animals with greater rapidity and ease than in others.   In the
horse it  requires a large amount of air to produce a  fatal effect.
He explained this as being due to the  strength of the right ventricle.
There is an observation of Berard which explains it better, especi- 
n6
ally if you bear in mind  some other observations to which I shall
refer.  This author states that the pulmonary capillaries in the horse
are much larger  than in  other animals.   There are other experi-
ments which show that if there is one thing pre-eminently necessary
for free capillary circulation, it is a proper density of the blood.  It
was not mentioned in the portion of the paper read by Dr. Senn,
that the injection  of water is capable of producing  symptoms iden-
tical to those produced by the injection of air, although, presumably
in the former  case, they pass away.  The only explanation of this
is a sudden alteration  in the density of the blood preventing it from
circulating in the capillaries of  the lung.   I think that the observa-
tion of Berard  in regard  to the size of  the capillaries of the horse,
in connection with the fact that we can inject relatively large quan-
tities of air into the veins  of these animals, and that the air is found
in the arterial  circulation, showing that spumous  blood will  pass
through the capillaries of the horse,  is  most important  in connec-
tion with the the-rapeutics  of this condition.
  I cannot think from the history of the cases and from the experi-
ments on animals, that death is a simple matter in air-embolism.  It
is due to a complication of causes, the chief being, I  think, anaemia
of  the centres  of respiration.   Dr.  Senn and  other experimental
observers  have thrown large quantities of air into  the heart, much
larger than could be  introduced in an operation before fatal  symp-
toms would come on.   Undoubtedly, in experimental cases, the
heart  is distended with air,  but this does not  obtain in the acci-
dental entrance of air into the venous circulation during operation.
The heart has  been found over  and over again not distended with
air.  It has been found to move with great force and strength even
after respiration has ceased,  so that death does  not come from the
heart,  but  from  respiratory  failure  due  to  deficiency of  arterial
blood in the centres  of respiration.   Undoubtedly the inability  of
the right ventricle to act properly is due not  only to the mass  of
spumous blood, which it  is unable to pass on through the lung
capillaries, but  also to the fact that the changes in  the density  of
the blood alters its physical conditions, and the valves  cannot be
forced back as they would  be by dense blood.   The result  is that
the blood is thrown  backward  and forward from auricle  to ven-
tricle.   Under  such circumstances the  removal of spumous blood
from the heart may be valuable.
  Dr. Senn  has called attention  to  the  chief facts, which  are ex- 
ii7
 planatory of the conditions favoring the entrance of air into the
 venous circulation, but there are others in operation which he does
 not note, such as the  position of  the  neck or arm, stretching the
 axilla in the various operations required in that neighborhood.  A
 slight amount of tension will  keep a vein open, so that  even the
 contractions of the platysma myotd  muscle will do so to  a certain
 extent.   Traction on a tumor will do the same thing.   There is
 another rare condition which  it is possible to conceive of, viz., the
 division of a vein in the angle of a wound.   As you raise the flaps
 you hold  that vein open and  effect  a  temporary canalization, and
 the evil results that follow this.
   Dr. Senn made the remark  that  in cases where air was  supposed
 to have been  generated in the blood, the observation  had been
 inaccurate, and that all the cases recorded were those in which free
 hemorrhage had  taken place,  and  in consequence there were open
 vessels where air  might have entered.  I dissent from that.  There
 are a certain number of cases where that explanation does not hold.
 I  had a case of my own which I cannot explain in any other way,
 and there are  a number of others on  record, occurring chiefly in
 the course of septicaemia.   I had a patient whose arm I had ampu-
 tated at the shoulder-joint.   Eight days later he sat up in bed appa-
 rently pretty well.   He gave a sudden exclamation, and before the
 nurse could reach him he was  dead.   I could get no post-mortem
 examination.   There was nothing  that would kill  him so quickly,
 except  air-embolism.   Deep  pressure  on the  stump forced  out
 bubbles of offensive gas.   There are  similar cases on record.
   As Dr.  Warren  has said, the preventive treatment is more im-
 portant than the curative.  We cannot carry our whole armamen-
 tarium around with us, and we are not likely to have an aspirator
 convenient.  I have always had a great dread of air-embolism, and
 there are certain things that I invariably aim to do in operating on
 the axilla or neck.  Thus, I think that complete anaesthesia is most
 important.  The sudden inspiration after a painful cut undoubtedly
 tends to draw air  in.  In passing,  I would allude to the fact men-
 tioned by Dr. Warren in reference to the sucking sound often heard
 during tracheotomy.  I have heard this sound frequently, and have
 been in times past much alarmed at it, but I have come to  the con-
clusion that it is due to the opening of the deep layer of the tracheal
fascia.   I have heard this sound when there  were no  open veins.
                               8* 
u8
It  is probably due to the same conditions which produce a similar
sound when air enters the axillary tissues.  Where anaesthesia is not
used the arms and chest should  be firmly bound down so that no
sudden inspiratory movement can be taken.   In removing a tumor
from the neck, I usually tie its deep attachments, or hold  them with
clamp forceps on the cardiac side, before twisting off the tumor.  If
it is possible I never make a cut where there is  any tension of the
cervical or axillary tissues, unless there  is a  finger on the cardiac
side of the vein.
  Should air enter, what can be done?  Experiment has shown that
artificial  respiration  in those cases where a non-fatal quantity of air
has been injected is of service.   This should be done in the recum-
bent position.  Air will not enter as readily in the recumbent posi-
tion as in the erect position.   The head should  be dependent, the
limbs raised, and  artificial  respiration  carried on,.   Treves  has
recently  suggested a method  for preventing further entrance of  air.
It may not be easy to tie the vein, but a wet sponge can be at once
squeezed, filling the wound with  water.   Then, as has been  shown
by experiments in animals and in the human subject where recovery
has taken place, the symptoms are  partly those of syncope.   The
arterial  blood should be diverted from  the  extremities to the brain
by  compressing  the  axillary and femoral  arteries.  This  expedient
probably also effects another purpose. It increases the intra-cardiac
pressure  so that it is  possible to have  the valves closed and  the
blood forced through the pulmonary capillaries.
  It is hardly necessary to say that  the  cardiac action should be
kept up by stimulation.  There is one suggestion that  I should  like
to  make, viz.,  in  addition to  the subcutaneous injection of ether
and the application of ammonia to the nostrils an^J so on,  we  should
use subcutaneous injections of  atropia.   If it is  true that the injec-
tion of larger quantities of air are required  to kill a horse, because
of  the larger size of the capillaries  in that animal,  the importance
of  dilating  the human pulmonary capillaries  to their fullest capaci-
ties is seen.  This is a secondary result of a  large dose of atropia.
It also stimulates the respiratory centres.  I have seen it do it.  I
reported  a  case last year in which the  pulse and respiration  had
ceased for about three minutes.  It was a case of brain abscess.  I
attributed the temporary recovery to the injection of atropia, life
being prolonged for six  days.   It  is indicated, and  it can  do no 
H9
harm.   It is true that atropia does depress the action of the heart
a little, but  you get more than a compensating  advantage by the
enlargement of the pulmonary capillaries.   Experience has shown,
that  if  the  patient can  be kept  alive for a  short  time he may
recover.  After recovery the patients  are  apt  to be  attacked with
secondary pneumonia, which is to be treated on general principles.

  Dr. Senn.  I am under great obligations to the gentlemen who
have so ably discussed my paper.   Their remarks bear evidence of
study and careful preparation.   In view  of  the numerous well-
authenticated  cases of sudden  death during surgical operations  it
requires no argument to prove  that  the  subject of air-embolism
should  be as  important  to the surgeon as the obstetrician.  The
very fact that so many surgeons have witnessed  this accident is a
strong argument in favor of discussing this subject at this time and
in this  place with a view of arriving at some  definite  conclusions
pointing towards preventing this occurrence,  or in case a danger- B
ous,  or fatal amount  of  air has  entered, what measures might  be
resorted to  to modify or annul its deleterious  effects.   The intro-
duction of a few bubbles of air does not produce death, because it
neither interferes with the passage of blood through  the pulmonary
circulation nor with the  perfect  mechanism of the  heart's action.
When air is  introduced slowly and  in small quantities, not sufficient
to arrest the  heart's action, it is  forced  through  the  pulmonary
capillaries into the left  side of the heart  and  arterial  circulation,
where it is brought into contact with an extensive surface for absorp-
tion, and  by its gradual removal sudden  accumulation in danger-
ous localities is  prevented.   A clicking  sound heard during  an
operation is no indication that air has entered a vein ; such a sound
may attend  the ingress of air  into any hollow space.  The  sound
produced by the entrance of air  into a vein  resembles  a sucking
sound, which is best expressed by the German word " schluerfend."
Muscular  contractions always produce compression of a vein, and
thus would rather tend to prevent, than to produce, entrance  of air.
When the necessary conditions are present to maintain the patency
of a vein  after incision  I consider  the elevated  position the most
important element in  causing the entrance  of air.  The experiments
on the superior longitudinal sinus reported in my paper sufficiently
corroborate this statement.  In  regard to the treatment by direct
aspiration of the right ventricle, which saved a good percentage of 
120
  the animals where a fatal dose of air had been administered, I must
  again emphasize the fact that over-distension of the right ventricle
  occurs  as much from  accumulation of  venous blood from the
  obstruction in the pulmonary capillaries as from the presence of
  air,  hence any procedure which can  remove  the cause of the  over-
  distension in the shortest space of time must be relied upon in pre-
  venting paralysis by over-distension.  The all-important indication
  presents itself to maintain the action of the heart until the obstruc-
  tion in the pulmonary circulation has been removed.   Death does
  not  take  place instantly.   The  heart  often  continues  to  contract
  feebly for some time, until  by accumulation of  blood in the  right
  ventricle over-distension results in arrest of muscular contractions.
  As aspiration  of the right ventricle in itself is not attended by any
  immediate or remote danger, I must insist that it  should always be
  resorted  to  in cases  of air-embolism  when other  measures are
  inadequate to prevent death  by over-distension and  paralysis of the
» heart.  Removal of air  from the right side of the heart by aspira-
  tion also  constitutes  the most direct measure in preventing death
  by asphyxia or acute  cerebral  anaemia, as it diminishes the number
  of air-emboli  which  otherwise would  subsequently pass into and
  obstruct the pulmonary  vessels.  The experiments have also shown
  the usefulness of venesection  in  these  cases, the beneficial effect
  being due to its direct effect  in preventing engorgement and disten-
  sion of the right side of the  heart.
    Air-embolism produces obstruction in the pulmonary vessels by
  bubbles of air becoming arrested in the vessels, which act, for the
  time being, like any  other kind  of emboli by mechanically inter-
  fering with the circulation.  In the  horse the  contractions of the
  right side  of the heart,  as compared with other animals, are  more
  powerful,  and on this account over-distension is  not as likely to
  take place, the air being forced  rapidly through  the pulmonary
  capillaries into the left side of  the heart.   Injections of air into the
  left side of the heart are less dangerous,  because the powerful con-
  tractions of the left ventricle are  more  competent to force the  air
  from the  heart  into the  peripheral circulation and  through the
  systemic capillaries.   A simple alteration  in the  density of the
  blood is  not  attended by such grave symptoms indicative of ob-
  struction in the pulmonary  circulation  as  we observe it after air-
  embolism.  Intravenous injection of a saline solution after sudden 
121
and  severe  hemorrhage is never  attended  or  followed  by such a
train of grave  symptoms as  we observe after the entrance of any
considerable quantity of air  into a vein.   Auto-transfusion, as sug-
gested  by Dr.  Nancrede, would, as he states, increase the intra-
cardiac pressure, and on this account I should be afraid to increase
the function of  an already over-distended organ.  The best possible
method to remove the cerebral anaemia is to diminish the intra-
cardiac pressure, as  by doing  so we  maintain  the action of the
heart until the obstruction in  the pulmonary vessels is removed, and
the  equilibrium  between  the  arterial  and venous  circulation is
restored.   Theoretically the use of atropia would  be  indicated ;
practically,  however, I should  expect a more prompt effect from
the inhalation of nitrite of amyl.
   In closing my remarks I  desire to thank the gentlemen for the
interest they have manifested in my paper, and for  the many valu-
able suggestions made. 
 
AN
EXPERIMENTAL AND CLINICAL
STUDY  OF AIR-EMBOLISM
N. SENN, M.D.,
          OF MILWAUKEE, WISCONSIN,
ATTENDING SURGEON TO THE MILWAUKEE HOSPITAL; PROFESSOR OF THE PRINCIPLES AND
  PRACTICE OF SURGERY AND CLINICAL SURGERY IN THE COLLEGE OF PHYSICIANS
           AND SURGEONS, CHICAGO, ILLINOIS.
LWr?
CO
ouorr&
■&?b
rak
<L
        Extracted from the
Transactions of the American Surgical Association,
        Vol. III. 1885
         PHILADELPHIA:
COLLINS, PRINTER, 705 JAYNE STREET.
            1885. 
 
 
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