Page:Popular Science Monthly Volume 84.djvu/577

Rh results have been mentioned above. Other experiments and writings confirmed, extended and defended his views. Bernard had made a great discovery and pushed it to the end and did not have to suffer the humiliation so often falling to the lot of a pioneer who pronounces a great fundamental truth and is outstripped by his contemporaries in producing proofs and developing details. Though it took several years to work out all the details, he always kept the lead.

This discovery supplied much that had been obscure concerning the sugar metabolism in the body and the functions of the liver, and greatly influenced general biological thought. It overthrew the idea that animals can not construct but only destroy products built up by plants. It broke down the prevailing theory that each organ has only one function. Previous work had shown that the liver produces bile and the pancreas and stomach furnish digestive juices. Nothing more seemed left to be learned except the function of the spleen. The discovery of the second function of the liver destroyed the bonds which the theory of functions had thrown around the biological thought of the time and encouraged more work in this field. The introduction of the idea of an internal secretion which was poured into the blood to assist in the normal nutrition of the body has been very productive and still fills the minds of physiologists and bids fair to produce some of the most valuable contributions to modern physiology.

Glycogen was soon found in all the tissues and quantitative relations were investigated. Others have contributed but little new to the subject and Bernard's ideas stand to-day as he expressed them then.

During this work, Bernard discovered the remarkable fact that a puncture of the fourth ventricle of the brain causes temporary diabetes. This, like other of his discoveries, was not happened upon accidentally, but was the result of logical reasoning concerning the nervous control of the sugar production by the liver, which he assumed to be a typical internal secretion. He found that cutting the vagus nerve stopped the sugar production and reasoned that stimulation of the nerve should lead to increased production. Being unsuccessful when all the ordinary means of nerve stimulation were used, he resorted to an expedient which he had noted previously, that a marked stimulation occurred when the point of origin of the nerve in the brain was punctured. In this case, an over-production and excretion of sugar was obtained. Here, as in a number of instances, a wrong view led him to an important discovery for he soon showed that the vagus is not a true secretory nerve governing the hepatic sugar secretion.

This illustrates one of Bernard's important characteristics. He