Page:Popular Science Monthly Volume 29.djvu/344

330 the duty usually fulfilled by an artery.' He suggested that this weak power, by which the portal vein propelled its blood, was compensated for by a suction force communicated to the current of the blood by the actions of respiration. These reasonings have been confirmed by certain experiments of M. Bernard." "In persons, then, who lead a sedentary life, this auxiliary force for promoting the circulation of blood through the liver is diminished, blood stagnates in the gland, and the functions of the organ are deranged, these results being all the more likely to arise if the liver be at the same time over-stimulated by errors in diet."

Take another organ. The stomach is a muscular organ, being furnished with bands of muscular fiber, which squeeze and press the food, turning it over and over, so that it may be the better permeated by the juices which digest it. It, too, is stimulated by exercise, especially by an exercise like walking or riding, which increases its movement. This motion makes easier work for the organ and increases its activity. It increases its activity also in another way, by demanding more of it. For increased work by any part of the body means increased destruction of tissue. "To repair the waste is the office of the blood, as the distributor of the material to be supplied. The main furnisher of this new material in the right form to do its work is the stomach. For food is both the fuel which keeps our bodily machinery going and the material by which the machinery itself is repaired. The stomach, with the duodenum, is the place where all this material is prepared to do its work in the most economical way. More exercise, then, means more waste, more waste means more repair, and more repair means a greater demand for food and water. The more, then, we waste any part of the body by exercise (within certain limits), if there is due repair, the better off is that part. The strength of the body, as a whole, and of each part of the body individually, is thus ever in relation to its newness."

The bowels, too, the great sewers of the bodily system, inclosed in pliable walls needing constant motion and fresh supplies of blood for their healthy exercise, feel the action of the breathing lungs, and are sensible of every turn, twist, rising, and falling of the body. Deprive the body of exercise, and you deprive the bowels of blood and proper action, and bring in a long train of evils, a catalogue of which can be read in the advertising columns of almost any daily newspaper.

The kidneys, too, are affected by physical exercise. Doubtless they receive a certain stimulation from the motion communicated to them in exercise, but as they are engaged in the work of eliminating from the system its excess of liquid with certain effete matter in solution, and as the skin is also concerned in a similar work, they are affected by exercise mostly with reference to this joint action. The more active the skin is, the less work the kidneys have to do.