RECENT PHYSIOLOGY. 89 



increases tlie 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 sub- 

 stance 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 con- 

 cerned in that movement. But while each motor center is thus con- 

 nected 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 afl'erent fibers with the muscles, the skin over- 

 lying 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 observa- 

 tions 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. 



