Page:Popular Science Monthly Volume 29.djvu/697

Rh for the arrival of this important part of its commissariat, the body receives such food-elements soon after digestion begins. The fats, starches, and sugars are, on the contrary, passed onward to be digested in the intestine. They become available for nutrition only after several hours of digestive work. The principle of "small profits and quick returns"—itself an economical and commercially satisfactory mode of doing business is illustrated in the digestive transactions of the body. That which is urgently required for the frame is quickly supplied, while the (in one sense) less important foods are left for later absorption.

In this economical work the liver plays an important part. Long ago in physiological history that organ was regarded simply as a bile making machine. The bile, thrown upon the food just after it leaves the stomach, was regarded as an all-important digestive fluid. To-day we have entered upon entirely new ideas of the* liver's work. As Dr. Brunton has aptly put it, the liver is no more to be regarded as a mere bile-maker than the sole use of an Atlantic liner is to be found in the manufacture and display of the water-jets which issue from the sides of the ship as the waste products of her engine-work. The liver is really a physiological constable placed at the entrance of the blood circulation. Into it are swept digested matters. These are further elaborated and changed so as perfectly to fit them for entrance into the blood. When the functions of the liver are suppressed or rendered inactive, elements of deleterious kind are apparently allowed to enter the circulation, and thus produce all the symptoms of the body poisoning itself. This being so, we begin to see that the bile is really a mere by-result of the liver's work, as the condensed water of the steamer is the consequence of the real function of the vessel. Bile is a waste product, and as such it is discharged into the intestine and thus excreted.

But natural economics rule life's actions here as elsewhere. For the apparently useless bile, Nature finds a use. It is discharged upon the food, and mingles with the half-digested nutriment. It has come to exercise a digestive or dissolving action upon fats, a function aptly illustrated by the household use of the "ox-gall" to remove grease stains in the house-cleaning periods of human existence. Moreover, the bile would appear to aid in promoting the muscular contractions of the intestine, and in thus expediting digestive action. It may possess other duties still; but enough has been said to show that the economy which rules living functions is probably nowhere better illustrated than in the utilization of bile, as a waste product, in the normal discharge of the digestive act.

Turning, lastly, to the nervous system and its work, we may find exemplified equally manifest phases of economical action. When we reflect upon the fact that higher life is a tremendously complex matter in its nervous and mental phases alone, we may well be tempted to