488 



VETERINARY PHYSIOLOGY 



pressure of oxygen is the great function of the blood pigment 

 in the body. The hcemoglobin plays the part of a middle- 

 man betiueen the air and the tissues, taking oxygen from 

 the one and handing it on to the other (Chemical Physi- 

 ology). 



Amount- — Hgemoglobin constitutes about 13 or 14 per 

 cent, of the blood, but in various diseases its amount is 

 decreased. 



Red. 



Yellow, 



Gkekn. 



Blue. 



Carbon-monoxide ~| 



Hsemoglobiu . > 



Oxyhaemoglobiu . J 



Haemoglobin. 



Methaemoglobin . ") 



Acid Hfematin . ( 



Carbon - dioxide C 



Hi«moslobin . ) 



Reduced Alkaline ) 

 Haematin . . i 



Fig. 199. — Spectra of the more important Blood Pigments and their more 

 important derivatives. (The spectra of oxyhiemoglobin and carbon 

 monoxide hemoglobin and those of acid h;ematin and nieth;T?nio- 

 globin are not identical.) The arrows indicate that oxyhemoglobin 

 and methemoglobin are changed to hemoglobin by reducing agents. 



The best method of estimating its amount is by Haldane's 

 Haemoglobinometer. This consists of two tubes of uniform 

 caUbre, one filled with a 1 per cent, solution of normal blood 

 saturated with carbon monoxide, and another containinsr 

 water in which 20 c.mm. of the blood to be examined, 

 measured in a pipette, are placed, mixed with coal gas to 

 saturate with CO, and then diluted till it has the same tint 

 as the standard tube. The percentage of haemoglobin, in 

 terms of the normal, is indicated by the mark on the tube 

 at which the fluid stands {Chemical Physiology). 



