206 THE HUMAN SPECIES 



The temperature of the blood in mammals ranges between 

 37 and 40 C., and in birds between 41 and 43 C. 



Important differences exist in the coagulation-times : 

 Human blood coagulates in 2-3 minutes 



Dogs, rabbits 4-5 



Pigs, oxen 8 



Horses ,,15 



The blood of birds, reptiles, amphibians and fishes takes 

 considerably longer to clot, vis., from two to eight days. 



The serum, which in all mammals contains O'6 per cent, 

 sodium chloride, is alkaline, and in man has a specific gravity 

 of 1028 (average). 



The haemoglobin in man and animals is identical in almost 

 every way. But there are differences, chiefly shown in 

 crystallisation : the crystallisation time and the form of the 

 crystals vary ; in man they are prismatic, in oxen and dogs 

 rhombic prisms, in horses flattened, in porpoises and rats 

 half pyramids (tetrahedra), in squirrels flat (hexagonal system). 



Quite recently Friedenthal discovered that the mixing of 

 blood of nearly allied animals is innocuous to the animal into 

 whom another's blood is injected, but that in non-allied animals 

 foreign blood so injected causes disintegration of the blood 

 corpuscles. The following interesting facts are quoted from 

 Uhlenhuth's : excellent account of his biological researches. 



When blood is introduced into the circulation of an animal, 

 certain specific products appear in the blood of the subject so 

 treated : 



i. A body which destroys the blood corpuscles haemolysin. 



ii. A body which causes them to run together and cohere 

 agglutinin. 



iii. A body which precipitates the albumin of the blood 

 precipitin. 



Upon injecting a rabbit with human blood a serum is 

 produced which will only react in this manner with human 

 blood. 



This method has been used to establish the blood-relation- 

 ship of various animals. Uhlenhuth has shown that the serum 

 from a rabbit injected with human blood will produce a pre- 

 1 Corr.-Blatt.f. Anihrofol., etc., 1904, pp. 114-18. 



