GENERAL VIEW OF THE ANIMAL FUNCTIONS. 95 



within it. Besides this, during the waste -of the active tissues in the 

 proper animal functions, the products of the decomposition of the 

 wasted substance of the muscular and nervous systems, and of their 

 dependencies, are drawn into the current of the circulation, and ren- 

 der the blood more or less impure. Its impurities, so derived, must 

 be thrown off; otherwise life would be extinguished, not by inanition, 

 but by an act of self-poisoning, either slow or rapid, according to the 

 nature and quantity of the impurity so retained in the circulating 

 fluid. 



Hence to maintain the balance between the necessary waste and 

 renovation of the body, to preserve the purity of the blood and the 

 integrity of the animal organs, and so render possible the due exer- 

 cise of the proper animal functions, certain other, and most complex, 

 functions require accordingly to be regularly performed. These, 

 which form one subdivision of the group of vegetative functions, are 

 named the nutritive functions. 



The animal, constrained to seek for food, seizes it by prehensile 

 movements, and introduces it into the interior of its body, exercising 

 thus the function of prehension of food. Such food is, however, un- 

 fitted, without due preparation, for actual entrance into the substance 

 or tissues of the animal, and is therefore subjected to certain special 

 processes, included in the general function of digestion, performed by 

 the alimentary canal and its appendages. First, the food, at least in 

 the higher animals and in man, requires to be bruised or comminuted 

 by the process of mastication performed by the' teeth, jaws, and mus- 

 cles, concerned in this act, aided by the tongue and cheeks. During 

 this reduction of the food, another process is necessary, especially 

 when the food is dry ; and that is, its admixture with a large quantity 

 of fluid matter, named the saliva, which is formed by the salivary 

 glands, and by aid of which the mass of food is rendered soft enough 

 to be swallowed, while certain of its ingredients are subjected even to 

 chemical change. This constitutes the process of insalivation. The 

 swallowing of the food, which is named the act of deglutition, is per- 

 formed by aid of the tongue, the part called the fauces, the pharynx 

 or back of the throat, and the oesophagus or gullet. From the lower 

 end of the gullet, the masticated and insalivated food is propelled into 

 the stomach, where it undergoes gastric digestion or digestion proper, 

 under the agency of the gastric juice, which acts chemically on certain 

 portions of the food, and aids in its solution, performing thus the pro- 

 cess of chymification. By certain movements of the stomach, the soft- 

 ened portion of the food, now named the chyme, is urged onwards into 

 the small intestine, at the upper part of which it becomes admixed with 

 the bile formed by the liver, and with the pancreatic juice yielded by 

 the pancreas. These fluids continue the chemical processes of change 

 and solution already commenced. It is also blended with the so-called 

 intestinal juice. After this, the pulpy mixture is fitted for the next 

 great vegetative function, characteristic of all organized bodies, viz., 

 the function of absorption, by means of which, the fluid and dissolved 

 parts of the food and drink at length enter into the substance of the 

 living animal, and ultimately gain access to the blood. This absofy- 



