Page:Popular Science Monthly Volume 59.djvu/99

Rh increases the rapidity with which fat is laid on. According to the recent researches of Loewy and Richter at the Agricultural College in Berlin, the explanation is that the ovaries produce a substance which hastens the oxidation of the tissues and the food. When this substance is injected below the skin of animals whose ovaries have been removed, the tissue waste is markedly increased.

In the domain of nervous physiology our knowledge is growing apace. The doctrine of the localization of function on the surface of the brain may now be considered as well established. The motor region has been subdivided into areas, each of which is related to a particular movement, because the nerve-fibers springing from the large pyramidal cells contained in it, are connected with nerve-cells in the gray matter of the spinal cord which send nerve-fibers only to the muscles concerned in that movement. But while each motor center is thus connected by motor or efferent fibers with the muscles, recent work by Sherrington and Mott and by other observers has shown that it is also connected by sensory or afferent fibers with the muscles, the skin overlying them, the joints in their neighborhood, and the bones which they move. The 'motor area,' in fact, is not purely motor, but has sensory functions as well.

No convincing proof has yet been given that any particular portion of the brain is exclusively concerned in intellectual operations. Goltz, the most prominent representative of the dwindling band who still refuse to believe in the localization even of the motor functions, has lately published an interesting paper containing the results of observations on a monkey which was carefully watched for eleven years after the removal of the greater part of the gray matter of the middle and anterior portions of the left hemisphere of the brain. The character of the animal, whose little tricks and peculiarities had been studied for months before the operation, was entirely unaffected. All its traits remained unaltered. On the other hand, disturbances of movement on the right side were very noticeable up to the time of its death. It learned again to use the right limbs, but there was always a certain clumsiness in their movements. In actions requiring only one hand, the right was never willingly employed, and it evidently cost the animal a great effort to use it. Before the operation it would give either the right or the left hand when asked for it. After the operation it always gave the left, till by a long course of training, in which fruit or lumps of sugar served as the rewards of virtue, it learned again to give the right. Evidently, although this is not the interpretation placed by Goltz upon his observations, the motor centers of the right side of the brain, which normally preside over the movements of the left side of the body, had to be laboriously educated before they became able to carry out such movements of the right hand.