SPECIFIC GRAVITY OF SERUM AND BLOOD. 23 



Our investigations have shown that the hlood is far less abundant in cold than 

 in warm-blooded animals. 



This fact is important, because it will aid us in the investigation of many of the 

 phenomena of cold-blooded animals, and in the explanation of the differences which 

 distinguish the two great classes of animals. 



Color of the Blood and Serum. 



The arterial blood of cold-blooded animals is never of that bright red color of 

 the arterial blood of warm-blooded animals, on account of the mixture of the 

 arterial and venous blood in the common ventricle of the heart. For the same 

 reason, the venous blood is not of so dark a color as that of warm-blooded animals. 



The color of the serum in most Reptiles — as Ophidians, Batrachians, Fishes-— 

 and some Chelonians — as the Gopher (Testudo £>olyp>hem.us) — is of a light yellow 

 color. 



In many carnivorous Terrapins — as the Yellow-belly Terrapin {Emys serrata), 

 Chicken Terrapin {Emys reticulata), and Salt-water Terrapin [Emys terrapin) — the 

 serum is of a golden color. 



In most Birds and Mammalia which I have examined, the serum is of a light 

 yellow color. In the Black Turkey-buzzard (Cathartes alratus), it is of a golden 

 color. 



Odor of Animals. 



The strong smell of both cold and warm-blooded animals appears to reside espe- 

 cially in the serum, and may be developed by treating the serum with a little sul- 

 phuric acid, and applying a gentle heat. I have demonstrated this fact in numerous 

 instances, and often in the serum of disagreeable animals, with disgusting power. 

 The odor of animals is also due, as in the Alligator and Rattlesnake, to peculiar 

 glands. The secretion of the anal gland of the Rattlesnake emits such a powerful 

 and disagreeable odor, that it may produce giddiness of the head and sickness of 

 the stomach. 1 



Specific Gravity of the Serum and Blood. 



These results were accurately determined upon the balance used in all my 

 analyses, which, as we have before stated, was capable of indicating j^^tli of a 



1 In dissecting a large male Rattlesnake (Crolahts durissus), I accidentally cut the anal gland, and 

 the odor was so peculiar, heavy, and disgusting, and exerted such an effect upon the head, that it was 

 with the greatest difficulty that the dissection and drawing were completed. 



