132 MRS, ERNEST HART, 
On the Micromerric Numpration of the Btoop-cor- 
PUSCLES and the Estimation of their HmMOGLOBIN. 
By Mrs. Ernest Hart. 
THE micrometric numeration of the blood-corpuscles and 
the estimation of hemoglobin are operations which, though 
of comparatively recent introduction, have rapidly passed 
out of the sphere of laboratory experiment into practical 
use as exact methods of physiological and clinical investiga- 
tion. Those who have worked at this subject cannot, how- 
ever, have proceeded far without discovering that the 
methods and instruments hitherto in use are inconveniently 
imperfect and vitiated by numerous sources of error. Some 
recent improvements by M. Malassez, assistant in the La- 
boratory of Histology in the Collége de France, appear to 
me to have done much to remove these disadvantages. 
Before proceeding, however, to describe the new Corpuscle- 
Counter which M. Malassez has just introduced, it may be 
well to say a few words on the methods and instruments 
usually employed for the numeration of the corpuscles. The 
three which have been hitherto in general use are those 
known as the instruments of Malassez, Hayem, and Gowers. 
In the method first invented by Malassez (the Compte- Globules 
Capillaire) 100 parts of a 5 per cent. solution of sulphate of 
soda are mixed in a special instrument called the Melangeur 
Potain (Fig. 1) with one part of blood. This solution is then 
drawn into an extremely fine capillary tube. The calibre 
of this tube is known ; hence the volume of the fluid which 
the tube contains in a given length, say in 500, 400, or 300 
micro-millimeters is alsoknown.! This volume is some frac- 
tion of acubic millimeter. It follows that the volume multi- 
plied by the denominator of that fraction will equal a cubic 
millimeter. The multiplier is written on a glass plate, on 
which the capillary tube is mounted. Before using the instru- 
ment the eye-piece of the microscope must be exchanged for 
an eye-piece containing a micrometer divided into a number 
of square millimeters. Then by means of a stage micro- 
meter, the microscope must be graduated, so that ten of the 
square millimeters of the eye-piece correspond exactly to 
the arbitrary length (500u, 400u, or 300m) fixed upon. A 
mark being then put on the tube of the microscope, this 
magnifying power—the lens being always the same—can 
be easily found again. The process and calculation are then 
1 This unit, the thousandth of a millimeter, is expressed by the Greek yu. 
