66 Kansas Academy of Science. 



this paper, i. e., that through tlie necessity of food to animals, modification necessary to 

 adaptation to the food used has taken place, and that through this adaptive modification 

 extensive difierentiation of animal structure has obtained, through the multii)licity of 

 food-changes. 



Given the presence of food, the first important function, tlie first action, indeed, per- 

 formed by the animal in its jirocurement, is prehension — the seizing and conveying of 

 the food to the organs of mastication and deglutition. The organs exercising this func- 

 tion are of wonderful variety, but in each species are specially adapted to the kind of 

 food employed. In Mamvialia, for instance, the organs of prehension are especially the 

 lips of the mouth, but which are further assisted in many species by other organs, as in 

 Bimana, Quadruinana, Bodentia, and Marsupialia, by the fore limbs; in the elephant, by 

 the proboscis; in the tapir, by the snout; in the ant-eater and giraffe, by the tongue, etc.; 

 and are supplemented, usually, by the teeth, for more forcible seizure and retention. 



The next function performed, is mastication. This is effected by the teeth, with their 

 supporting environments — the jaws, muscles, etc. This region is, perhaps, the most 

 readily susceptible to food-changes, and the influence of food-selection. It is the gate-, 

 way to the economy upon which the entire alimentary system depends for the nutrient 

 substances that maintain life. It is the set of millstones through which all food must 

 pass, and by whicli all food must be reduced into digestible form. The masticating region 

 is the most variable of the entire organism, and presents more variety, taken throughout 

 the whole animal world, than any other special region of the economy. The cause of 

 this mutability of structure we assume to be due to the influence of food-selection, exer- 

 cising its power in modifying the parts with which the food comes so forcibly in contact, 

 on entering the animal system. The masticating apparatus mu.st be adapted, preemi- 

 nently, to the food employed, for upon the adjustment to the work of reducing it, every- 

 thing depends. Modification and re-modification in conformity to food-changes is a 

 constant law of the being and usefulness of this region ; and this has indeed obtained 

 through the long ages, until the contemporary result in our own time is a wonderful 

 variety of forms of masticating apparatus. Tliis is the Avork of food-seleCtion — a con- 

 formity of tools to material, not of food to organs. 



In the further okservation of the animal organization, we find the same adaptation. 

 Throughout the length of the alimentary canal, in the deglutition, digestion, solution and 

 assimilation of food; in all the processes whereby the food used is converted into nutri- 

 ent pabulum for the support of the life and growth of the tissues, evolution has per- 

 formed the work of perfect conformation of the organs to the food as employed. As 

 evidence in point, we may note the diflference between the stomach of a ruminant and a 

 carnivore, employing highly specialized forms of extensive classes for examples. In the 

 ruminant the many compartments into which the stomach is divided, the lengthy intes- 

 tine, and the complicated process nece.ssary for the elaborate digestion and solution of 

 vegetable food, is in marked contrast to the simple stomach and alimentary system of 

 the carnivore, whose food ( being animal tissue already converted from the vegetable ) 

 requires the merest dissolving pi-eparatory to absorption and assimilation. In the rumi- 

 nant the long intestine presents an extensive absorbing surface to the slowly-dissolving 

 bolus of vegetable tissue ; while in the carnivore, the intestine is short, as ab.sorption of 

 its food is cliieffy performed in the stomach, and a long intestine is useless. This is in 

 keeping with the fact that animal food is chiefly dissolved and absorbed in the sac of the 

 stomach, and vegetable, starchy foods are acted upon and absorbed in the intestine. In 

 omnivorous animals, as man, for a mixed diet we find a mixed capacity, while in vege- 

 table feeders and carnivora of all grades, these organs are adapted to the food used. 



But let us glance at some other forms as peculiarly adapted to their food, as employed, 

 and the apparent causes for modification. 



