108 



GENERAL CONCLUSIONS. 



matter for absorption. We have previously stated that, in the pancreas of this 

 remarkable fish we have conclusive proof of the function of this gland. 



2. The pancreas of carnivorous fishes and reptiles is relatively much larger than 

 that of frugivorous Chelonians. This difference in the relative size of this organ 

 in these two classes, is evident at a glance. In the Ophidians it is a compact, ovoid 

 gland, and in the carnivorous Chelonians it is a broad, lobulated, well developed, 

 conspicuous gland; whilst in the frugivorous Gopher {Testudo polyphemus) it is a 

 thin, delicate, obscure gland, composed of several slender lobes, subdivided into 

 numerous lobules. 



3. The pancreas of carnivorous Mammalia is much larger than that of the frugivor- 

 ous or granivorous. The principal exception to this assertion appears in the Beaver, 

 which is stated to have an unusually large pancreatic gland. A consideration, how- 

 ver, of the character of the food of this animal will, we think, explain this anomaly. 

 The stomach, and more especially the caecum of the Beaver, is stated by observers 

 to be filled up with fragments of bark and wood, which appear to constitute its 

 chief aliment. The experiments of Mitscherlich have shown that alkaline solu- 

 tions are capable of converting cellulose into starch, even more readily than con- 

 centrated acids. It is, therefore, highly probable that the great office of the alkaline 

 pancreatic fluid in this animal is the preparation of cellulose for absorption, by con- 

 verting it into starch. 



4. The pancreas of carnivorous fishes and reptiles is larger than that of frugivor- 

 ous and granivorous mammals, notwithstanding that the digestion of the former 

 is much slower than that of the latter, and the amount of nutritive matters necessary 

 to sustain the economy much less. 



5. The pancreas of carnivorous mammals is larger than that of carnivorous 

 cold-blooded animals ; the digestive process is much more rapid, and correspondingly 

 larger glands are needed to supply the secretions necessary for the proper preparation 

 of the food for absorption. 



The difference between the weights of the organ in these two classes of animals, 

 does not correspond exactly with the disparity of their respective digestive processes, 

 probably because the sluggish circulation and aeration of the blood, and the small 

 amount of nervous force possessed by cold-blooded animals, require much larger 

 organs to accomplish precisely the same results. As circulation and respiration 

 are developed and perfected, and all the acts of life rendered correspondingly active, 

 the more perfect and condensed become the organs and apparatus. 



These results were shown, as far as simple dissection and inspection, upon other 

 animals killed in swamps and woods, and at periods when it was impossible to 

 ascertain their weights. 



Our investigations upon birds have not been sufficiently extended to warrant 

 general conclusions. 



Whilst experimenting upon the effects of starvation and a change of diet upon 

 the blood of carnivorous terrapins I found, as stated in a previous chapter, that the 

 pancreas of many of those which had been deprived of food and drink for a length 

 of time, and then placed in a tub of water and liberally supplied with vegetable 

 food was diseased. Parts of the gland were of a black color and hard texture, and 

 under the microscope contained cancer-like cells and crystals which resembled in 



