. A text-book of animal physiology, with introductory chapters on general biology and a full treatment of reproduction ... Physiology, Comparative. DIGESTION OF POOD. 299 Before passing on to higher groups, it will be well to bear in mind that the digestive organs are to be regarded as the out- come both of he- Si > "â ifcTWl â¢- câ ^ P o H^ e *⢠s o & 3 aj-o redity and adap- tation to circum- stances. We find parts of the in- testine, e. g., re- tained in some animals in whose economy they seem to serve little if any good purpose, as the vermiform ap- pendix of man. Adaptati
. A text-book of animal physiology, with introductory chapters on general biology and a full treatment of reproduction ... Physiology, Comparative. DIGESTION OF POOD. 299 Before passing on to higher groups, it will be well to bear in mind that the digestive organs are to be regarded as the out- come both of he- Si > "â ifcTWl â¢- câ ^ P o H^ e *⢠s o & 3 aj-o redity and adap- tation to circum- stances. We find parts of the in- testine, e. g., re- tained in some animals in whose economy they seem to serve little if any good purpose, as the vermiform ap- pendix of man. Adaptation has been illustrated in the lifetime of a single indi- vidual in a re- markable man- ner ; thus, a sea- gull, by being fed on grain, has had its stomach, nat- urally thin and soft-wajled, con- verted into a muscular giz- zard. Since diges- tion is a process in which the mechanical and chemical are both involved, and the food of animals differs so widely, great variety in the alimentary tract, both ana- tomical and physiological, must be expected. Vegetable food must usually be eaten in much larger bulk to furnish the needed elements; hence the great length of intestine habitually. Si§1Shi '.Â¥ IVI-a? 5 CQ qo p <u 1 oiS e8«M gS^ <u*C f. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Mills, Wesley, 1847-1915. New York, D. Appleton
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