Page:Popular Science Monthly Volume 84.djvu/575

Rh and absorbed much lower down than was the case when it was fed to dogs, and soon found that the variation was due to the different points of entrance of the pancreatic duct into the intestine in the two animals. This led to a long series of experiments on the function and properties of the pancreas. He showed for the first time that the pancreas and not the stomach was the chief organ of digestion and that the gastric juice merely started the digestion which was completed by the more powerful pancreatic juice. Its three-fold function for digesting proteins, fats and carbohydrates was also demonstrated. For this work, which was reported in 1848-9 and published complete in 1856, Bernard was awarded the prize of experimental physiology by the Académie des Sciences and was introduced to the scientific world as a physiologist of remarkable ability and great promise.

The story of the discovery of glycogen, which revolutionized prevalent biological theories concerning functions of the organs and differences between plant and animal metabolism, is interesting in showing how a quick, alert mind can "grasp the hints that Nature gives" and advance, step by step, to a final realization of the complete truth.

The prevalent view concerning the differences between plant and animal metabolism had been proposed by Dumas, the chemist, and Boussingault, the agronomist. They showed that plants build up complex organic compounds from inorganic substances and animals, by feeding, take the complex compounds already formed and break them down to simpler ones. Animals might modify them, but never make them more complex. There was a complete cycle in which compounds were built up by plants and broken down by animals. While this was the prevalent view, there were some strong minds who opposed it. Liebig confirmed Huber's old observation that bees, fed on sugar alone, produce wax and showed that fattening geese accumulate fat in excess of the fat fed.

Bernard proposed to trace the successive steps by which the various food-stuffs are transformed in the body and chose sugar as the subject for his first investigation because it seemed liable to the simplest explanation. The other foodstuffs were never investigated. He was early interested in diabetes and wished to find the cause for the excess of sugar in the blood and thereby assist in working out a remedy. His plan was as follows:

He had shown that cane sugar must be changed before it can be retained by the blood. Tiedemann and Gmelin had proved that starch is changed to sugar before it is absorbed from the alimentary tract. This indicated to him that all carbohydrates enter the blood as simple sugars. Where was this sugar destroyed? If he could find the tissues that caused the destruction and by some means decrease their activity, the blood would become overloaded with sugar and experimental