A TREATISE ON ELEPHANTS. 
(2) Pancreatic juice is the secretion of the pancreas ; it is a 
clear slimy fluid containing two ferments, one a protein-splitting 
ferment, which completes the work begun in the stomach, and the 
other, a starch-splitting ferment similar in its action to ptyalin but 
more powerful. 
There is also a fat-splitting ferment present which breaks up the 
fats into their component parts and aids in their absorption. 
(3) The intestinal juice is a pale yellow-coloured fluid secreted 
by various glands in the lining membrane of the intestine, and 
containing a ferment which assists the pancreatic juice in various 
ways but principally by splitting peptones and many other proteins 
into still simpler bodies. 
Movements of the intestine. — The intestine being composed of 
involuntary muscle tissue, its movements are of the wave-like variety 
and assist in passing the food along. 
During its passage along the intestine the proteins, fats and 
carbohydrates are absorbed, and what remains is thrown out as 
faeces. The food absorbed is carried along by the blood stream 
and distributed to the tissues as we have seen. It may be used 
immediately as a source of energy for the production of work and 
heat and for the repair of tissues, or it may be stored in the body 
for future use ; in most animals this storage takes place in the fatty 
tissues, so that when the usual supply of food is cut off for any 
reason, the animal uses its own stored materials and tissues. This 
is shown by the animal losing weight. In starvation, etc., the first 
tissues to go are always the fatty tissues. 
Respiratio7t. — All animals require oxygen ; in mammalians this 
is taken from the atmospheric air, and the process is called 
respiration. The process of respiration consists of two parts : — 
( 1 ) The passage of air into and out of the air cells of the lungs. 
(2) The interchange of gases between the air in the air cells 
and the blood in the lung capillaries. 
The atmospheric air is composed of two gases principally, namely 
oxygen and nitrogen, in the proportion of 2 i parts of the former to 
79 parts of the latter; nitrogen is incapable of supporting life and 
its use seems to be to dilute the oxygen. 
(i) Passage of ai}' into and out of the lungs — Is brought about 
by the movements of expiration and inspiration. 
The act of inspiration is a muscular act brought about by the 
muscles of the chest, the resting position of the chest being that of 
expiration. Ordinary expiration is mainly a passive act, being 
simply the return of the chest to the position of rest, but sometimes 
voluntarily or involuntarily expiration may be forced and in this 
case the act is partly due to various muscles. The chief of these 
