32 MICROSCOPIC EXAMINATION OF THE BLOOD. 



Alexander Schmidt determined the weight of the red blood-corpuscles in 100 

 parts of blood in the following manner: He ascertained (i) the percentage of dry 

 residue of the blood = T; (2) the percentage of dry residue of the corresponding 

 blood-serum = t; (3) the dry residue of the erythrocytes contained in 100 grams 

 of blood = r; the dry residue of the serum obtained from 100 grams of blood is 

 then T r, the corresponding amount of serum - ; further, the weight 



of the erythrocytes in 100 parts of blood = 100 - ; the latter equals 



48 grams in 100 grams of blood from a man and 35 grams in the same amount 

 of blood from a woman. 



Number. In men the number of red blood-corpuscles is more than 

 5,000,000, while in women it is about 4,000,000 in i cubic millimeter, 

 making 25 billions in 5 kilos of blood. The number is in inverse pro- 

 portion to the amount of the plasma, and from this fact it will be seen 



FIG. i. A, human colored blood-corpuscles: i, on the flat; 2, on edge; 3, rouleau of colored corpuscles. B, 

 amphibian colored blood-corpuscles: i, on the flat; 2, on, edge. C, ideal transverse section of a human 

 colored blood-corpuscle magnified 5000 times linear: ab, diameter; cd, thickness. 



that the number must vary in accordance with the state of contrac- 

 tion of the vessels, conditions of pressure and diffusion - currents 

 and the like. 



The number of red blood-corpuscles is increased in venous blood (at times 

 in small cutaneous veins and in the presence of stasis) , after the ingestion of solid 

 food, after rest at night, after marked loss of water through the skin, the intestine 

 or the kidneys, during inanition (in consequence of the consumption of blood- 

 plasma), in the blood of the newborn, at times after late ligation of the umbilical 

 cord (from the fourth day the number again becomes reduced) , in persons of 

 vigorous constitution and in residents of the country. The number is dimin- 

 ished during pregnancy and after copious libations. The capillaries contain 

 relatively few blood-corpuscles. Apparent increase or diminution must also ac- 

 company variations in the amount of plasma, and to this fact special attention 

 should be given in investigating the effect of certain influences upon the number 

 of erythrocytes. Thus, for instance, the increased number observed in those re- 

 siding at a high altitude may depend, wholly or in part, upon a greater or lesser 

 reduction in the plasma. In the earlier stages of fetal life the number is from J 

 to i million in i cu. mm. 



Method of Counting Blood-corpuscles. An exact mixing apparatus for the 

 dilution of the blood is the first requirement. For this purpose the mixer of 

 Potain will answer (Fig. 3). This is a carefully calibrated, pipet-like glass instru- 



