3
i^uou<^
                          ON THE

EXTENT OF THE PLEURA ABOVE THE  CLAVICLE.

                    By 0. E.  Isaacs, M.D.,

  DEMONSTRATOR OP ANATOMY IN THE  UNIVERSITY OF THE CITY OP NEW YORK,
      CONSULTING SURGEON TO BLACKWELL's ISLAND HOSPITAL, ETC., ETC.

                      READ APRIL 1, 1857.
  If the question were asked of any well-informed physician
or surgeon, What is the extent of the pleura above the clavicle,
or,  what are the height and width of the pleural sac in that
situation? he would probably answer, that the pleura g°^rally
rises about an inch, or perhaps even an inch and a half, above
the first rib;  that its width here was variable or uncertain ;
and that he was not even sure that  it usually reached above
the clavicle, and  if so, only to a slight extent.  I shall here
quote  some of  the  best anatomical authorities, in  order to
exhibit the present state of information upon this subject.
  In speaking of the upper portion of the pleura, Horner says:
"In proceeding along the first rib, which is very oblique, it
forms a sort of bulging  bag, which projects  towards the tra-
chea, lines the lower part of the scalenus anticus muscle, and
receives the upper extremity of the lung.  In order to under-
stand well the position of the pleura, it mast be borne in mind
that the upper rib is placed very obliquely downward and for-
ward, at an angle of  forty-five degrees with the spine—conse-
quently the  pleura, on being reflected from its whole internal
edo-e, is much higher at the head of the rib  than it is at the 
4
On the Extent  of the
anterior extremity of the same/'—Horner's Anat., vol. ii., pp.
165-7.
  According to Cruvelhier,  " the  pleura above  is  reflected
beneath the first rib, and terminates  in a cul de sac, intended
for the reception of the apex  of the lung,  and projecting more
or less above that rib."—Cruvelhier, vol. i., p. 549.
  Sharpey and Quain state that "the upper part of the pleura,
which receives the apex of the corresponding lung, projects, in
the form of a cul de sac, through the superior aperture of the
thorax, into the neck, reaching an inch, or even an inch and a
half above the margin of the first rib, and passing up between
the lower end  of the scaleni muscles—a  small slip  of which,
arising from the transverse process of the last  cervical vertebra,
is described by Mr. Sibson as expanding into a dome-like apo-
neurosis or fascia, which covers or strengthens the pleural cul
de sac, and  is  attached to the whole of the  inner edge of the
first rib.   The right pleura is generally stated to reach higher
in the neck than  the left; but  in 20 cases  recorded by Mr.
Hutchinson, the right lung was higher than the left in 10 cases,
and the left higher than the right in 8, while in 2 the height was
equal on  the  two sides.  Owing  to the height  of the dia-
phragm on the right  side,  the right pleural sac is shorter than
the left; it  is at the  same time wider."—Vol. ii., p. 950.
  Harrison  says " the pleura  ascends  as high  as the transverse
process of the  sixth or seventh cervical vertebra.  The pleurae
are  of a  conical form.   The apex of each is in  the neck,
covered by the scalenus anticus,  and the subclavian artery.
The apex of the right is often higher in the  neck than that of
the left.   The  apex of the lung, when distended,  rises in the
neck to a height varying from one  to two  inches above the
level of the first rib.  The apex of the right  is usually higher
than that of the left.
  According to Von Behr, "  the pleura costalis projects above
and over the first rib  and the apex of the  lung."— Von Bear's
Anat, p. 219.
  In Allen's Dissector it  is stated that " the pleura is prolonged
from half an inch to an inch above the first rib, where it covers
the  posterior surface of the lower part of the scalenus anticus 
Pleura above the Clavicle.               5
muscle, and the subclavian artery.  It  usually extends  some-
what higher on the right side'than on the left."—Allen's Dis-
sector, p. 296.
  Wilson remarks that " the pleura covers the thoracic surface
of the vessels, at the root of the neck, extending for somewhat
more than an inch above the margin of the first rib."— Wilson's
Dissector, p. 306.
   I  have consulted the Encyclopedia of Anatomy,  Bourgery
and Jacob, Sibson's Medical Anatomy, the works of Meckel,
Husche, Theile, Velpeau, Blandin, Malgaigne, and many  others,
without finding any more  information upon the  subject.  Not
the  slightest mention is made of the extent of the pleura above
 the  clavicle.
   Having been aware, for some years past, of the great height
 to which the pleura sometimes extends above the clavicle, and
 of the practical bearing of this  fact, I consulted at that time
 many  of the  works already quoted, but to my surprise met
 with the result already stated.  As I continued  occasionally to
 observe this arrangement of the pleura in the neck, it  seemed
 to me that this point was of sufficient importance  to demand
 investigation, and I shall  here  give the  result  of examination
 of one hundred subjects, in which I have endeavored to use all
 possible care and precaution, so as to ensure accuracy in every
 observation.   The following method was adopted:
    The subject being placed upon the back upon a firm  table,
 the thorax was opened in the usual manner, by cutting through
  the cartilages of the ribs, and either sawing or breaking through
  the sternum, near its junction  with the second rib.  The next
  step was to  ascertain that  the body was squarely  and evenly
  placed upon the table, the arms lying easily and evenly by the
  sides, and the head, neck, and upper extremities  put into as
  natural position as  possible.   Care was also taken, in  measur-
  ing the extent of the pleura, not to disturb the parts any more
  than  could be  avoided.  One hand was then  introduced into
  the thorax, and into the superior  part of the pleural cavity,
  above the clavicle, and this was carefully  examined.   By the
  other hand,  applied upon the  skin, the opposite fingers of the
  hand first introduced could easily be felt through the inter- 
6
On  the Extent of the
 vening tissues, and the height and width of the pleura readily
 ascertained and measured.
   In cases where there was any doubt or difficulty in gaining
 the measurement, I passed with one hand long needles, firmly
 fixed in handles, downwards and backwards through the integ-
 uments, so as to strike the superior and lateral edges of the
 pleural sac,  while, with  the  lingers of  the other hand intro-
 duced into the  pleural cavity, I ascertained that the needles
 were correctly placed.  By  these methods there  could hardly
 be a possibility of error in the measurements.  As the superior
 part of the  pleural sac is generally prolonged above the  first
 rib and  clavicle, in a dome-like  form, the  measurements were
 accordingly taken with reference to its  shape,  and so as  to
 ascertain the following points :
   1. The height of the sternal or  inner  edge  of the pleura
 above the clavicle.
   2. The height of its central portion.
   3. The height of its outer edge.
   4. The distance of the sternal or inner edge of the pleura
from the median line.
   5. The distance of the outer edge of  the pleura from  the
median line.


[Several diagrams, and dried and recent preparations from the
  dead subject, were here exhibited.']
  I  recorded  each  observation  in  a book,  and  cautiously
abstained from  reading, or comparing what I had  written
until I had obtained  the desired number of one hundred cases.
This was done in order that I might  not be influenced in my
measurements by any preconceived  notions; and  I. may  add
that some of the conclusions,  to  which it  was impossible to
arrive until after a long and tedious reckoning up of the whole
number of observations,  were entirely different from  what I
had  anticipated.  I  have made a table of  the one hundred
cases, copied from the record: 
Pleura  above the Clavicle.
EXTENT OF  THE PLEURA ABOVE THE  CLAVICLE
                            IN  100 SUBJECTS.
HEIGHT OF THE PLEURA ABOVE THE CLAVICLE.
LATERAL EXTENT  OF
 THE PLEURA ABOVE
 THE CLAVICLE.
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1. Male
2.
8.   "
4.
5. Female
6. Male
7.
8. Female
9. Male
10. Female
11.
12.
18. Male
14. Female
15.
16.
17.    "
18.    "
19.
20. Male
21.
24. Female
25.
26.   "
27.   "
28. Male
29.
80. Female
81.
82. Male
88.
84. Female
85. Male
86.   "
87.   "
88. Female
89   *'
40. Male
41. Female
42. Male
43.
44.   "
45. Female
46.
47.   "
48. Male
49.   "
50. Female
51.   "
Black
Mulatto
White
Mulatto
White
Black
White
Black
White
Mulatto
White
Black
White
Mulatto
Black
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On  the Extent  of the
HEIGHT OF THE PLEURA ABOVE THE CLAVICLE.
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LATERAL  EXTENT  OF
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 52. Male
 53.
 54. Female
 55. Male
 56. Female
 57. Male
 58. Female
 69.   "
 60.   "
 61. Male
 62.   "
 63.   "
 64.   "
 65. Female
 66.
 67. Male
 68. Female
 69. Male
 70. Female
 71.
 72.   "
 78.
 74. Male
 75.   "
 76.   "
 77.   "
 78.   "
 79.   "
 SO. Female
 61.
 82. Male
 83.
 84. Female
 85. Male
 86.
 87.   "
 88. Female

 9o! Male
 91.   "
 92. Female
 98.   "
 94. Male
 95.
 96. Female
 97. Male
 98. Female
 99. Male
100.   "
	Right.	Left.	Right.	Left.	Right.	Left
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Black	i		1	i	i	*
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(i	li		14	14	li	1
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«'	li		2	11	li	li
«'	1		H	11	1	i
"	li		1J	H	14	li
"	li		li	n	li	l
»	l		li	i	li	1
"	0	li	0	2	0	U
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Mulatto	2		2	n	2	l
White	li		2	ii	2	14
"	li		14	u	14	14
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"	li		24	U	2	11
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"	n		2	H	2	11
"	ii		2i	11	2i	2
«c	14		li	li	14	li
"	li		li	2	li	li
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"	1 , 1		14	14	14	li
"	li ' 1		14	14	li	14
"	14		14	li	1	li
"	1		li	H	li	H
♦'	li		U	li	14	14
"	H		li	14	li	1|
"	14		H	U	i	1
"	H		2	H	2	i
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"	14		li	2	14	2
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White	1		2	li	14	l
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If	Si	24
J	24	24
II	»i	3
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i	3	84
1	24	84
11	«*	3
1	24	24
H	24	8
f	3	84
14	24	21
t	8	84
1	2i	2S
i	34	8
1	S4	3
14	Si	8
4	«i	84
4	3	24
1	3	8
i	2|	24
1-	3	3
1	Sf	24
1	3	3
4	24	24
1	2*	8
1	2+	24
*	24	24
4	3	3
4	3	3
4	4	84
14	3	8
1	84	84
4	2*	24
1	n	34
1	Si	84
0	2t	2
4	«4	8
u	«4	34
1	3	84
4 1	4i	4
                               REMARKS.

In No. 4, the pleura on the right side extended 1} inches to the left of the median line.
In No. 7, the pleura on the left side was only a little above the first rib.
In No. 8, the pleura on each side was only slightly above the first rib.
In No. 22, the right pleura extended one inch to the left of the median line.
In case 28, the right pleura extended half an inch to the left of the median line.
In No. 27, the right pleura extended J of an inch to the left of the median line '
In No 34, the pleura extended upwards only to  the upper margin of the clavicles.
No. 35 was similar to 84. 
Pleura  above  the Clavicle.
9
  In No.
  In No.
  In No.
  In No.
  In No.
line.
  In No.
  In No.
  In No.
  In No.
  In No.
line.
41, the pleura on the right side extended one Inch to the left of the median line.
42, the pleura on the right side extended I of an inch to the left of the median line.
43, the pleura on the right side extended one inch to the left of the median line.
46, the pleura on the right side extended £ of an inch to the left of the median line.
49, the pleura on the right side extended one inch and a quarter to the left of the median

51, the pleura on the right side extended half an inch to the left of the median line.
54, the right pleura extended one inch and a quarter to the left of the median line.
, 55, the right pleura extended one Inch to the left of the median line.
 66, the pleura on the right side did not rise above the superior margin of the clavicle.
 67, the pleura on the right side extended one inch and a quarter to the left of the median
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go S «	>	>3	rH q	The pleura is wider on the right side by 0.87 of an inch.
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Distanc Outer E Pleura Median	bo	o s4	Thed between sides is of an in
 
10                 On the Extent of the
       COMPARATIVE  HEIGHT  AND WIDTH
OF THE PLEURA  ABOVE  THE CLAVICLE, IN THE  MALE  AND THE
  FEMALE, CALCULATED FROM MEASUREMENTS IN 47 MALES AND
  47 FEMALES.
	HEIGHT OF THE PLEURA.						WIDTH OP THE	
								
Sex.	Sternal Edge of		Central Portion of		Outer Edge of the			
	the Pleura.		the Pleura.		Pleura.		PLEURA.	
	Right.	Left.	Right.	Left.	Right.	Left.	Right.	Left.
Male....	1.23	1.042	1.53	1.29	1.25	0.35	2.64	2.06
Female..	1.12	0.85	1.40	1.21	1.14	0.97	2.36	1.93
	Tho pleura,		The pleura,		The pleura,		The pleura,	
	in the male, is		in the male, is		in the male, is		in the male, is	
	0.11 higher on		0.13 higher on		0.11 higher on		0.48 wider on	
	the right side,		the right side,		the right side;		the right side,	
	and 0.192 on		and .08 on the		but on the left		and on the left	
	the left.		left.		side it is higher in the female by 0.12.		by 0.13 of an inch.	
  It is thus seen, from these measurements, that the pleura in the male is not
only higher, above the clavicle, but also wider, in that situation, than it is in the
female.
  Before presenting this table, however, I may here .remark
that the top or upper extremity of the pleural cavity does not
present a regular or dome-like form  in  all instances, as  is
described  by  anatomical authorities.   On  the  contrary,  it
sometimes forms culs de sacs, which extend upwards, like the
fingers of a glove, into the recesses of the neck.   Sometimes
also,  these are  prolonged  laterally  from the  right  pleura
extending across  the median line  to  the  left side,  and pass
upwards, either between the bodies of the cervical  vertebrae
and the oesophagus, or between the  oesophagus and the trachea.
  I exhibit here:
  1. A TABLE  OF  100 CASES.
  2. Average table.
  3. Table of the height and width of the pleuka, in  the
male and female. 
                 Pleura above the Clavicle.              11

   4. The high extent of the pleuka.
   5. TueIow extent of the pleura.
   6. The sternal edge of the right pleuka.

                High Extent of the Pleura.

   In 14 cases, the pleura on the right side rose to the height of
 two inches and upwards above the clavicle, and in only one
 of these cases to two inches and a half, which was the greatest
 height  observed in  any instance.  In 5 cases only, the pleura
 on the  left side rose to the height of two inches.  In 4 cases,
 the pleura on both sides extended to the height of two inches
 and upwards above the clavicle.  It will thus be seen that, in
 100 cases, the pleura rose two inches and upwards above the
 clavicle, in 14 cases on the  right side, in 4 on the left, and on
 both sides in 5—in  all, 23 cases—thus giving in 100, the pro-
 portion of nearly one in four.
   I have repeatedly shown several of these cases to Drs. ¥m.
 H. Van Buren,  George A. Peters, J. W. S. Gouley, George T.
 Elliot, James  M. Minor  of Brooklyn, and  many others, who
 were satisfied,  from their own examinations of the subjects,
 that the measurements were correctly made, and as stated in
 this paper. I  beg leave to express here my thanks to my
 friend, Dr. Gouley, for his valuable assistance in the measure-
 ment of many subjects.

                Low Extent of the Pleura.  .

   There were  only  five cases in which the pleura did not rise
 above the superior margin of the clavicle.  In No. 7 (a white
 male), the pleura on the right side was of the usual height, but
 on the left it only rose a  little above  the first rib. In No. 8 (a
 white female),  the  pleurae  on  both  sides were only slightly
 above the  first rib.   In No. 34 (a white  female), both pleurae
 only reached the upper margin  of the clavicle.  In No. 35 (a
 white male) a similar arrangement  existed.   In No. 66, the
pleura on the right side  extended to the upper margin of the 
12                  On  the Extent  of the

clavicle; on the  left it was higher than usual.   This was in a
white female.
             Sternal Edge of the Bight Pleura.

  The  sternal or inner edge of the pleura on  the right side,
extended across and to the left of the median line  in 11 cases.
Thus it was to the left of the median line—
		
22......	......i	ii
27......	......*	ii
41......	......1	it
42......	......*	u
43......	......1	u
46......	...... i	u
49......	......li	u
51......	......\	u
54......	......li	u
55......		u
  These cases are necessarily  included in the calculation  of
the width of the pleura, in the whole number of subjects.  In
these 11  cases,  if  we  measure  from  the sternal, or  rather
inner edge of the pleura, to its outer  margin, we obtain the
width of the pleural sac in  this situation.   Owing to its inner
edge extending across the median line, and to the opposite
side, the width of  the pleura was unusually great in these
cases.  It is recorded in inches and decimals.   It was__

                  In case  1............4.25
                         2............4.25
                    "    3............3.75
                    "    *............4.
                    "    5........ ... 3.66
                    "    6............4.
                    "    1............4.25
                    "    8............4.
                    "    9............ 3.75
                    "   10............4.50
44.11 
Pleura above the  Clavicle.
13
  The average width  of the pleura in these 11 cases was  4
inches.   This  fact is important in reference to the surgery of
this region, as, in 100 cases, one in every 9 presented the pecu-
liarity of great width of pleura.
  It has thus been shown  that, in 100 cases, the pleura rose
only to  the upper margin of the clavicle, or very  slightly
above it, in 5  instances; that in 11 cases the right  pleural sac
extended across and to the left of the median line, making an
average  width of the pleura, at this point, of four inches; that
a similar arrangement never was  observed on the left side;
that in 23 cases the pleura ran  high, extending two inches and
upwards above the clavicle, thus giving an average proportion
of one in four; that in 14 instances this occurred on the right
side, and in only 5 cases on the left, and  on both sides in 4;
that in one case only, the  pleura  attained the height of two
and  a half inches above the clavicle; and  that the height and
width of the pleura are both greater in the male  than in the
female.  These  facts,  then, are  of value  to  the physician,
because  the apex of the lungs corresponds with the concavity
of the pleural sac above  the clavicle, and it is important for
him to ascertain its extent,  if practicable, by auscultation and
percussion.  They are  also useful to the surgeon, in the  removal
of tumors, and in other operations in this region.
  In addition  to what  may  possibly be discovered by ausculta-
tion and percussion, are there any other means of ascertaining
the  height of the pleura during life ?  I may mention  that I
have generally noticed that the pleura rises highest  in those
who have long necks, while the reverse is the case in short, and
especially bull-necked  subjects.  I regret  that I have not kept
a full record of cases, with reference to this point.   I find, how-
ever, in looking over my notes, 12 cases marked as having long
necks, and in 10 of these the  pleura was  high.  In 11 short-
necked  subjects, the pleura was  very low in  3,  and in the
remaining 8 was below the  average height.
  In connection with  some facts already stated, I  may ask,  Is
it not possible that  certain cases  of death from operations  in
the  lower  part of  the neck  have  been  attributed to  the
entrance of air into the  veins, when, in  reality,  the pleural 
14                 On the Extent of the
cavity has been opened?  If this had been done at  a point
two inches or more above the clavicle, it  would  have been
supposed  that  it was here  tod  high  for  the  pleura to be
wounded.  The knowledge of the fact that penetrating instru-
ments  or gun-shot can enter the pleura at the point just men-
tioned, may  be of service  in the diagnosis, prognosis, and
treatment of  such injuries, and also in cases of  medical juris-
prudence.

  I now proceed to speak of a most  important point in  the
surgical  anatomy of  the upper  portion of the pleural sac,
which is its relation with the subclavian artery.  This artery,
for the purpose of description, may be  divided into three por-
tions :
  1st. That part of it which, on the right side, extends from the
bifurcation of the  arteria innominata,  or on the left, from  the
arch of the aorta, to the  inner margin of the scalenus anticus
muscle.  This portion of the artery is said to be within  the
scalenus  anticus muscle, or inside of the same  muscle.  This
portion of the  artery always rests on the pleura, and  this fact
adds much to the difficulty and danger of ligating the artery
at this point.   The anatomy of the subclavian arteries within
the scaleni muscles, is more complicated than that of any other
surgical region of the human body.  Notwithstanding the dif-
ficulty and danger of ligating the artery in this situation, it has
been tied, on the right side, firstly by Colles, next by Dr. Valen-
tine  Mott, whose  operations on  the arteria innominata,  the
common, external, and internal iliac, and other great arteries,
are forever  recorded among the  most  brilliant achievements
and triumphs of surgery.
  The subclavian was afterwards ligatured by Hayden, O'Reilly,
Partridge, Liston, and Auvcrt.  This  operation  has been per-
formed nine times, but has never succeeded,  owing  to  the
great  number  of  anastomosing  branches  sent  off from  the
artery, and which do  not allow of the formation of an internal
clot, but more  especially from the extension of the aneurismal
disease to the coats of the artery  at the point of ligature, and
the consequent occurrence of secondary hemorrhage. 
Pleura above the  Clavicle.
15
   In addition to the complicated relations of the artery on the
 right side, we find that the left subclavian, within the scaleni,
 is more deeply seated, and is in dangerous proximity to the
 thoracic duct.  The left  subclavian has only once been liga-
 tured within the scaleni muscles.  This exceedingly difficult
 and dangerous operation, which  reflects so  much credit upon
 American  surgery, was performed by Dr. J. Kearny Rodgers,
 in the New York Hospital,  in 1845.   An  account of it was
 published in the New York Journal of Medicine, in the March
 No. of 1846.  It  is much to be regretted that this operation,
 like the others upon the right  side, did not succeed.
   2d. The second portion of the subclavian artery is that which
 lies between the scaleni muscles, or under the scalenus anticus.
 This muscle and the artery are always, at this point, in contact
 with the pleura.
   The artery has been tied successfully, in this situation, by
 Dupuytren, Liston, and Warren, of Boston.
   3d. The  third portion  of the  subclavian  artery, which is
 the one commonly ligated for axillary aneurism, extends from
 the outer edge of the scalenus anticus to the lower margin of
 the first rib.  The brachial plexuj of  nerves is above, and  to
 the outside  of the artery—the subclavian vein is behind  the
 clavicle, and anterior to the artery.  The artery, in  this third
 portion of  its course, does  not  rest upon the pleura; and yet it
 is a fact, not mentioned by anatomical  authorities, but which I
 have  often had occasion  to  notice, and which any one can
 easily verify for himself, that when the pleura rises high in the
 neck, above  the  clavicle, it  carries with it  the  subclavian
 artery.  Throughout  its whole course, therefore, this  artery
 will correspond with the height of the pleural sac in this situa-
 tion.  Now, in the twenty-three cases mentioned in this paper,
 the subclavian artery was high in the  neck, and in  many of
 them this artery, in the third portion of its course, rested upon
 the pleura for a very considerable extent.
  I shall give the recorded measurements only of a few cases :
  1. In  one  case in which the pleura  rose very high in the
 neck, I found that one inch and a quarter of the right carotid,
three-fourths of an inch of the left carotid, and one inch and a 
16                 On the Extent of the
quarter of the third portion of the right subclavian, extending
from  the  outer margin of the scalenus anticus to the upper
edge of the first rib, rested upon the pleura.
  2. The third portion of the right subclavian, to the extent of
one inch, was in contact with the pleura.
  3. The third portion of the right subclavian, to the extent of
one inch and five-eighths, rested upon the pleura.
  4. The third portion of the right subclavian was in contact
with the pleura to the  extent of one inch and a quarter.
  5. The third portion of the left subclavian, to the extent of
one inch and five-eighths, rested upon the pleura.
  I have often taken measurements of similar cases, of which,
however, the notes have not been preserved.
  It is  on the  right side that we most frequently meet with a
high arrangement of the pleura, and a corresponding elevation
of the subclavian artery, inasmuch as in one hundred cases the
pleura was high  above the clavicle in twenty-three.   In all
instances, as is well known, the areolar tissue, of variable firm-
ness and density,  intervenes between the subclavian artery and
the pleura.  Notwithstanding this, should an operator who was
unaware of this occasional relation of the artery to the pleura,
attempt to pass an aneurism-needle around it in this situation,
without due  caution, he might  easily  tear or open into  the
cavity of the pleura.   It is  not improbable that this accident
may have occurred, and caused a sudden and fatal termination,
which was attributed to entrance of air  into the veins.
  The facts, then, which have just  been stated, are evidently
of great importance, yet I find, on  consulting the anatomical
writers  already quoted, nothing satisfactory upon this subject.
Nor have I  been more successful  in  obtaining information
from  the  surgical works of  Malgaigne,  Velpeau, Blandin,
Sedillot, Chelius, Pirrie,  Miller, the  Coopers, Gibson, Fer-
guson, Syme, Liston, Druit, Bourgery, and many others.
  In Mr. Guthrie's work on the arteries, I find the following
remark, while speaking of the ligature of the third  portion of
the subclavian :  "• The aneurism-needle  should be passed from
below upwards, by which the pleura will  be avoided."  (Arte-
ries, p. 39.)  From this observation, it would seem that he con- 
Pleura above the  Clavicle.               17
 siders that the artery is constantly in  contact with the pleura
 in this situation, which, however, is far  from being the ease.
 The caution which he advises is, nevertheless, very necessary,
 inasmuch as we have seen that the artery is high in the neck,
 in about the proportion of  one in four -cases, and would then
 rest upon the pleura.
   Mr. Erichsen says : " One principal danger in ligaturing the
 subclavian artery, at any point above the  first  rib, certainly
 arises from interference with the fine cellular tissue which  lies
 between it  and the scalenus muscle, separating it from  the
 pleura.   If inflammation be excited in  it,  the morbid action
 will  readily  extend,  by mere continuity of tissue,  into  the
 thorax by the anterior  mediastinum, invading ultimately the
 pleura and pericardium.  Hence, when it  is practicable,  the
 surgeon should keep the point of  the needle close to that part
 of the  artery which  lies upon the first rib,  as there is less  risk
 here of opening into the deep cellular tissue of the neck."
   He also states  that  inflammation  of the contents of  the
 thorax proved fatal in nine out of twenty-two cases of  ligature
 of the subclavian, in the third portion of its course—the pro-
 portion of deaths being  one  in two and a half.  This inflamma-
 tion, then, is the most frequent cause of death from this operation.
   He further  remarks:  " It will at first be supposed that, in
 this respect, the operations  on  the subclavian resembled other
 of the  great  operations of which pneumonia is  so common a
 sequel, but, on closer examination, it will be found that this is
 not the case—that the inflammation attacking the thorax, or its
 contents, after ligature of this  artery for axillary aneurism, is
 not confined to the lungs, but very commonly affects the pleura
 and pericardium, as well or  even in preference to these organs.
 It would, therefore, appear probable that it arose from causes
 essentially connected with this disease or operation."
   These he thinks are:
.   1. Inflammation of the deep cellular tissue, at the root of  the
neck, extending to the anterior mediastinum, pleura, and peri-
cardium.
   2. Pressure of the sac, which, by encroachment, gives rise to
inflammation of the pleura.
                              2 
18                 On the Extent of the
  3. Injury of the phrenic nerve.
  The single remark of Mr. Guthrie, and those of Mr. Erichsen,
comprise all the information upon this point which I have been'
able to collect from  the writers on surgery.  They say nothing
about the pleura in its  relation to the third portion of  the
subclavian artery—the part upon which a ligature is usually
applied.

  In conclusion, it  may be well to consider  what facts and
deductions have been adduced in  this paper, which may be
considered as new, or of an original character :
  1.  A table of 100 cases has been given of the extent of  the
pleura above the clavicle.
  2.  A table of the average extent  of the  pleura  in  the total
number of cases.
  3.  A  table  of  the  comparative  height  and width  of  the
pleura,  in the male and in the female, calculated from  the
measurements of 47 males and 47 females.
  4.  A  table of the cases in which the pleura rose high above
the clavicle.
  5.  A  table  of cases  in which the pleura only  reached  the
upper margin of the clavicle, or was very slightly  above it.
  6.  A  table of cases in which the sternal edge  of the right
pleura extended to  the. left, and across the median line.
  7. A  table  of  the width of the pleura, which is always
unusually great in such cases.
  8. The curious fact  that  the top of the  pleural sac is  not
always dome-shaped, but sometimes forms culs de sacs, extend-
ing upwards, and sometimes laterally, into the recesses at  the
root of  the neck.
  9. Conclusions drawn  from the occasional great height and
width of the pleura, which may be  valuable to the pathologist,
and to the medical  and surgical practitioner.
  10. Conclusions  drawn from the fact that the subclavian .
artery,  in the third division  of  its course, occasionally rests
upon, or is in contact with the pleura.  This  has  been shown
to occur in nearly one  case out of four.
  11. That the pleura rises high in the neck, above the clavicle, 
Pleura above  the Clavicle.
19
in long-necked  persons;  and, on the contrary, is low in short-
necked, and especially in very bull-necked subjects.
  12. Finally, it is believed that the facts and deductions which
have been stated in this paper, may be found to be interesting
in an anatomical, physiological, and pathological point of view,
and  of some utility in the practice of medicine and surgery,
and  in cases of medical jurisprudence;  and with this  hope,
they are respectfully submitted to the better judgment of this
Academy.