260 THE ANIMAL. XII. 



The solid portion of coagulated blood consists chiefly of red 

 and white corpuscles entangled in a net- work of fibrin. 



The red corpuscles consist usually of circular, biconcave 

 discs. In birds, amphibia, fishes, and some few mammals, 

 e.g., the camel, they are elliptical and biconvex. Their size 

 varies considerably in different animals, being largest in the 

 amphibia. In man they have an average diameter of -007 to 

 -008mm. ( = about -g-^uu inch) and a maximum thickness of 

 -0019mm. They are heavier than the plasma, having a specific 

 gravity of about 1 - 09. 



The average number in the blood of man is about 5,000,000, 

 in that of woman about 4,000,000, per cubic millimetre. By 

 treatment with water, ether, or other substances, blood cor- 

 puscles lose their colouring matter and leave a residue known 

 as the stroma of the red corpuscles. This consists of nitro- 

 genous matter and often retains the form of the original 

 corpuscles. 



The colour of blood depends upon hemoglobin and its com- 

 pound with oxygen oxy haemoglobin. Haemoglobin consists 

 largely of albumin (about 96%), the other characteristic com- 

 ponent being a colouring matter known as h&mochromogeri 

 (about 4%), containing iron. 



Haemoglobin from different animals differs somewhat in 

 composition. Haminarsten gives the following analyses : 



It has been calculated that the molecular weight of haemo- 

 globin must be about 14,000, and a formula which would 

 represent the composition of haemoglobin from the dog has 

 been given as C n ^B. m ^ m lPeSf^ m . Haemoglobin has the power 

 of uniting with oxygen, with carbon monoxide, or nitric oxide. 

 The stability of the compounds is in the order named and each 

 compound appears to be composed of one molecule of haemo- 

 globin with one of the gas. 



