44 



CHEMICAL PHYSIOLOGY. 



until the tint of the dilution is the same as that of the 

 standard. The amount of water which has been added (i.e., 

 the degree of dilution) indicates the amount of haemoglobin. 



Fig. 8. A, Pipette bottle for distilled water ; B, capillary pipette ; C, 

 graduated tube ; D, tube with standard dilution ; F, lancet for 

 pricking the finger. 



" Since average normal blood yields the tint of the standard at 

 100 of dilution, the number of degrees of dilution necessary to 

 obtain the same tint with a given specimen of blood is the per- 

 centage proportion of the haemoglobin contained in it, compared 

 to the normal. For instance, the 20 c.mm. of blood from a 

 patient with anaemia gave the standard tint of 30 of dilution. 

 Hence it contained only 30 per cent, of the normal quantity of 

 haemoglobin. By ascertaining with the hsemacytometer the cor- 

 puscular richness of the blood, we are able to compare the two. 

 A fraction, of which the numerator is the percentage of haemo- 

 globin, and the denominator the percentage of corpuscles, gives 

 at once the average value per corpuscle. Thus the blood men- 

 tioned above containing 30 per cent, of haemoglobin, contained 

 60 per cent, of corpuscles ; hence the average value of each cor- 

 puscle was g or of the normal. Variations in the amount of 

 haemoglobin may be recorded on the same chart as that employed 

 for the corpuscles." 



" In using the instrument, the tint may be estimated by holding 



