VII.] ESTIMATION OF HAEMOGLOBIN. 6 1 



In practice it will be found that, during 6 or 8 degrees of dilution, 

 it is difficult to distinguish a difference between the tint of the 

 tubes. It is therefore necessary to note the degree at which the 

 colour of the dilution ceases to be deeper than the standard, and 

 also that at which it is distinctly paler. The degree midway 

 between these two will represent the haemoglobin percentage." 



ADDITIONAL EXERCISES. 



8. Fleischl's Haemometer. This apparatus (fig. 36) consists of a horse-shoe 



stand with a pillar bearing a reflecting surface (S) and a platform. Under 



the table or platform is a slot carrying a glass wedge stained red (K), and 

 ved by a wheel (R). On the platform (M) is a small cylindrical vesse 



vessel (G), 



T 



FIG. 36. Fleischl's Haeniometer. 



divided into two compartments (a and a') by a vertical septum. In one 

 compartment is placed pure water, and in the other the blood to be investi- 

 gated. A scale (P) on the slot of the instrument enables one to read c 

 directly the percentage of haemoglobin. 



(a.} Fill with a pipette the compartment (a') over the wedge with distilled 

 water, and see that the surface of the water is quite level with the top of the 

 cylinder. Fill the other compartment (a), that for the blood, about one- 

 quarter with distilled water. 



