A MODIFICATION OF HEDIN’S HEMATOKRIT. 
BY 
W. F. ARNOLD, M.D., 
PASSED ASSISTANT SURGEON, U. S. NAVY. 
FROM 
THE M EDICAL N E W S, 
September 29, 1894. [Reprinted from The Medical News, September 29, 1894.] 
A MODIFICATION OF HEDIN'S HEM ATOKRIT } 
BY W. F. ARNOLD, M.D., 
PASSED ASSISTANT SURGEON, U. S. NAVY. 
I do not know that there is any necessity to 
apologize for bringing up this matter when the 
direct references to it in the English medical litera- 
ture accessible to me are contained in Von Jaksch’s 
Clinical Diagnosis,z and the New York Medical 
Journal, February 3, 1894, p. 151. The latter 
reference gives an abstract of the contents of a 
paper by Dr. Judson Daland, read before the New 
York Academy of Medicine on January 16, 1894, 
to which I refer those interested for nearly all 
the practical information extant upon the subject. 
Dr. Daland, with Dr. Carl Sadler, of Prague, has 
for some time been collecting data relating to the 
instrument, in the ultimate usefulness of which he 
expresses an abiding faith on what appeals to me 
as a most rational basis. 
My own irregular mode of life, almost devoid of 
free moral agency, from the very nature of my posi- 
tion, has prevented me up to the present time from 
adding any connected observations to those cited. 
I can only state that I have found the estimates of 
1 Read before the San Francisco Bacteriological Society 
August i, 1894. 
2 Charles Griffen & Co., London, 1893, p. 25. 2 
the numbers of the corpuscles by percentage-volumes, 
as given by Dr. Daland, correct within the limits 
assigned by him in the comparative estimations that 
I have made, using the Zeiss-Thoma hemocytom- 
eter j but these have been few in number, and 
not in all cases above reproach as to the exactness 
of their technical performance. 
I hope to be able to make a number of observa- 
tions upon the members of the crew of the U. S. 
Coast-Defense vessel Monterey, and upon oppor- 
tunity to extend them so as to include pathologic 
blood-states; but this is a matter of conditional 
promise, and, like obiter dicta, of little binding 
force and effect. 
On February 15, 1894, I devised a modification 
of Hedin’s instrument, substituting rubber blocks 
for the springs used to hold the tubes in place and 
to prevent leakage; it is shown in Fig. 1, in place 
upon a small electric motor hereinafter to be de- 
scribed. 
It was with this now discarded design that nearly 
all of my observations have been made. I think it 
satisfactory as an hematokrit of the kind promul- 
gated by its originator; and I believe that the 
further modification that I have introduced, of 
measuring the heights of the columns of corpuscles 
by direct reading with low powers ( X 200 or less) of 
the microscope from the limb graduated for record- 
ing the lateral motion of the mechanical stage, 
instead of the set graduations upon the tubes con- 
taining the diluted blood, is really an improvement 
worthy of the name. The method of taking the 
reading is shown in Fig. 2, the microscope resting 3 
Fig. i. 
Fig. 2. 4 
on a support upon the edges of its stage and of its 
foot, to prevent bevelling of the tops of the columns 
of the corpuscles, which occurs in other positions, 
from gravitation. Of course, some forms of micro- 
scopic stands will not lie in this position, but very 
little ingenuity would obviate this difficulty. 
Within the past week, considering the sources of 
error introduced and the trouble involved in the 
process of transferring the diluted blood from the 
capillary tube, for measuring and mixing, to the 
tubes of the hematokrit, I have designed a frame 
capable of receiving and holding during rotation 
the tube for measuring and mixing itself. This is 
shown in situ in Fig. 3, which is a reduced working 
drawing, complete even to the conventional hatch- 
ings for the representation of composition, of rub- 
ber, and of glass. For this refinement I am in- 
debted to a messmate, Passed Assistant Engineer G. 
S. Willits, U. S. Navy, who has made both the 
frame and this drawing of it. 
Fig. 3. 
With this arrangement the blood is diluted, and, 
after thorough mixing in the bulb, the capillary 
portion of the tube is filled with the mixture to its 
tip and placed in the frame and secured upon the 5 
motor, or upon the train of gearing for rotating. 
The result of effective rotation will be that all of 
the fluid above the center of form of the tube (its 
tip being considered as the lower end) will run into 
the bulb and that part of the tube above it, while 
the longest possible column of blood (for a given 
length of tube) of constant length and of absolutely 
exact dilution will be separated into its particulate 
and fluid components. 
Then, either the graduations on the tube, or the 
microscope and its mechanical stage (and I prefer 
the latter as more nearly conforming to the best 
scientific methods of measuring with great accuracy), 
may be used to get the percentage-volume. The 
capillary tube that I employ is that furnished with 
the Zeiss-Thoma apparatus for counting the colorless 
blood-cells. There is no reason why the finer tube 
supplied for counting the red blood-cells should not 
be used instead. I employ the first named because 
it is more easily cleaned. 
I am sorry that my experience does not enable me 
to speak definitely about the best diluent to be used. 
Separation is certainly easy with solution of potas- 
sium bichromate (2.5 per cent, strength, recom- 
mended by Daland1 as the best of nineteen fluids 
tried); but I have found a liberation of gas—pre- 
sumably oxygen—to be associated with the use of 
this, and it has proved troublesome by disturbing 
the layer of the colorless corpuscles. I have seen 
large bubbles rise and carry a line of red cells high 
into the supernatant liquid when the tube was under 
microscopic observation as depicted in Fig. 2. 
1 Loc cit. 6 
By most fixing-solutions, such as Hayem’s, separa- 
ration is made impossible. 
Coagulation vitiates the results in all cases in which 
it occurs, by entanglement of the cells in the meshes 
of the fibrin and by the bulk of the fibrin itself. 
It would be a great aid if it could be prevented 
by some vaporous agent, which would obviate the 
necessity of diluting the blood. 
It would be a great mistake to imagine that, using 
blood thus diluted, the layer of colorless blood-cor- 
puscles will obtrude itself upon the notice of even 
a reasonably careful observer. It is not, at least in 
normal blood, nearly so wide as a church door; and 
it is best described as a cream-colored or buff-colored 
tip upon the comparatively long column of red 
blood-corpuscles. Daland1 indicates briefly this 
indefiniteness. I have found Muller’s fluid, deeply 
tinged with methyl-violet, to aid somewhat in differ- 
entiating the layer of colorless corpuscles. It has 
the disadvantage of coloring the blood-plaques, 
which would, in that event, vitiate the result in pro- 
portion to their number. Daland says that this 
occurs in the absence of stains, or rather he notes 
a case in which the blood-plaques proved a source of 
annoyance. 
Obviously, therefore, this instrument cannot re- 
place the hemocytometer, which, with all its faults, 
will remain a claimant for interested favors, if not 
of affection, at our hands. But it may save time, 
and the great nervous strain inseparable from count- 
ing the squares, by indicating those cases that un- 
1 Loc cit., and American Journal of the Medical Sciences, vol. 
cvii, p. Si i. 7 
equivocally demand its assistance. Personally, I have 
never found any employment so irksome as the accu- 
rate use of this excellent instrument of precision; 
hence I am willing, at the risk of imputation of lazi- 
ness to myself, to allow electricity to remove this 
irksomeness, if it can be done (as I think it can be) 
in a perfectly trustworthy manner. 
I hope sincerely that some of the gentlemen of 
the Bacteriological Society of San Francisco, or 
others of the medical profession to whom this 
product of enforced idleness may come, will find 
the subject of sufficient interest to enlist their aid 
in determining the limitations and the usefulness of 
the principle embodied in the instrument described. 
My own clientele is limited perforce to men so care- 
fully selected that dyscrasise, such as leukocythemia, 
should not, and as a matter of fact do not, often occur; 
so that the best results I could secure under excep- 
tionally favorable conditions would deal only with 
states of comparative health, and these seem to be 
of the least importance of all the data necessary for 
the present status of the hematokrit, and its early 
establishment as a factor for constant use in diag- 
nosis. 
A word regarding the motor shown in Fig. i, 
which is one-half size; it is, I believe, the in- 
vention of a New York dentist, and its resem- 
blance to the gyroscope is apparent, the limbs 
of the moving part of that toy being the magnets, 
and the spindle upon which they revolve the shaft 
of this machine. The analogue of the frame of the 
toy is here the armature, composed of “ soft ” iron, 
and the presence of the current in it adds to the 8 
efficiency of the motor very decidedly, but in a 
manner not easily explicable, so electricians inform 
me. It will run at a speed of from 1200 to 2000 
revolutions per minute in circuit with an ordinary 
incandescent lamp ; and four Daniell or bichromate 
cells, or any good cautery battery, will drive it well 
with a fair load. I have used it for two years for 
centrifugal separation in urinalysis and for the little 
use I have made of Charcot’s and Luys’ miroir 
rotaiif. It may be obtained from Frank Wilks, 
Scott’s Wharf, Newport, Rhode Island, to whom I 
am indebted for much valuable information, and 
whose thoroughness as a designer and as an accom- 
plished artisan it affords me much pleasure to ac- 
knowledge. 
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