S8 EFFECTS OF THIRST, ETC., ON EMYS TERRAPIN. 



The fixed saline constituents were diminished, hecause they do not exist in so 

 large an amount in the Purslain (Porlulacva oleracea) as in the Small Reptiles, 

 Fishes, Crustaceans, and Mollusca, which constitute the ordinary food of these 

 Chelonians. 



In many instances, the shells of the Terrapins suffered from the deprivation of 

 the fixed saline constituents. They were rendered much softer. 



A deprivation of these constituents would prove much less injurious to cold- 

 blooded animals than to warm-blooded. 



In the latter, all the vital and chemical actions are rapid and incessant, and the 

 integrity of the nervous and muscular systems depends in a great measure upon the 

 supply of certain inorganic salts, as the phosphate of lime, which enter into their 

 anatomical composition, and are absolutely essential to their existence and the per- 

 formance of their functions. The action of the nervous system is always attended 

 with a corresponding consumption of the inorganic as well as the organic elements. 



In cold-blooded animals, the nervous system, circulatory and respiratory appa- 

 ratus, are feebly developed, and the metamorphoses of the organic and inorganic 

 elements of the tissues and organs are correspondingly slow. 



The effects of a change of diet were strikingly exhibited in the alterations of the 

 digestive apparatus. 



The intestines of carnivorous Chelonians are small and contracted. See Fig. 8, 

 which represents the digestive apparatus of the Snapping Turtle (Chelonura ser- 

 pentina). In frugivorous Chelonians, as the Gopher (Tesludo polyphemus), they are 

 large and capacious. (See Fig. 9.) 



This is not surprising, since vegetable substances are much more bulky, contain 

 much less nutriment, and are much more slowly digested than an equal amount of 

 animal food; and hence we might infer that the small intestines would be enlarged, 

 so as to render them suitable for the digestion of vegetables. 



In many cases, as already stated, the pancreas was affected with a cancerous 

 disease. One of the principal offices of the pancreatic fluid, is to form an emulsion 

 with fats, and I have found the pancreas to be always of a much smaller size in 

 frugivorous animals than in the carnivorous. It is probable that the gland, not 

 being normally exercised, degenerated in structure. 



Another marked effect in a change of diet, was the production of dropsical effu- 

 sions into the cellular tissue, the pleural and abdominal cavities. The vegetable 

 albumen of the Purslain was in a much more diluted form than that derived 

 from flesh, consequently a much larger amount of water was thrown into the cir- 

 culation than with a diet of animal food. The kidneys, called upon to perform 

 an unusual amount of work, were unequal to the task. Water, holding albu- 

 men in solution, accumulated in the cellular tissues and serous cavities. Gradu- 

 ally, however, the kidneys became accustomed to the change, and threw off more 

 perfectly the large amounts of liquid. The Terrapins examined shortly after their 

 removal to the tub of water, contained much more fluid in their tissues and serous 

 cavities than those examined after the lapse of some time. This shows us the 

 manner in which the characters of the blood are preserved. The watery elements 

 absorbed along with the Purslain did not accumulate in the bloodvessels, but were 



