MICROMETRIC NUMERATION OF THE BLOOD-CORPUSCLES. 14] 
lous care necessary to ensure correct and reliable results will 
not be thought trivial. 
Corpuscle counting is, however, only one stage in the 
optical investigation into the state of the blood. ‘To arrive 
at an opinion on which diagnosis and treatment should be 
based, it is necessary to estimate the amount of hemoglobin 
as well. In an elaborate paper! of Malassez (of which I 
published an abstract in the ‘London Medical Record’ of 
1879), all the various methods employed for estimating 
hemoglobin are described at length. In nearly all of these 
an arbitrary standard of colour is taken as normal, and the 
blood to be examined is compared with it. In Malassez’s 
Hemochromometer there is no arbitrary standard; each 
degree of the coloured standard solution to which the blood 
is compared corresponds to a blood containing a certain 
estimated amount of hemoglobin per cubic mm., and having 
the power of absorbing a certain known amount of oxygen. 
These figures have all been ascertained by a prolonged 
series of experiments; here therefore, there is no guessing 
that the amount of hemoglobin may be above or below the 
normal, for we are able to ascertain the actual amount of 
hemoglobin in a cubic mm. of. blood, and also the respira- 
tory power of the same unit. But M. Malassez points out 
that it is not only necessary to ascertain the amount of 
hemoglobin per cubic mm., but that we should learn in 
what state of division it exists, namely, what is the amount 
contained in each corpuscle. Welcker considers that there 
is always a constant relation physiologically between the 
richness of the blood in corpuscles and in hemoglobin ; 
Hayem and Johann Duncan have, however, discovered that, 
pathologically, particularly in anemia and chlorosis, the 
relations are disturbed, the number of corpuscles often rest- 
ing normal, the hemoglobin being less than normal. The 
way of arriving at the amount of hemoglobin per cor- 
puscle is, by M. Malassez’s method, extremely simple. The 
number of corpuscles in a cubic mm. of blood is first 
counted, and by the hzemochromometer the amount of 
hemoglobin per cubic mm. is estimated. The latter figure 
divided by the former gives the amount of hemoglobin per 
corpuscle. ‘[Thus, a blood containing 5,000,000 corpuscles 
per cubic mm., and 0°125 mlgr. of hemoglobin per mm. 
gives 5050000 = ‘000,000,025 mlgr., % €. a.50 000 of a 
000,000 Of a gramme, or, as it is commonly written, 
1 «Sur les diverses Méthodes de Dosage de L’Hémoglobine et sur un 
nouveau Colorimétre,” par L. Malassez, ‘ Arch. de Phy.,’ 1877. 
