WHERE AND HOW WE REMEMBER. 613 



to be connected by means of insulated white nerve-fibers with the eye. 

 The area which, one says, governs touch, the other says is connected 

 with the skin. The area which one proves to be concerned with vol- 

 untary movements, the other finds to be joined to the muscles. Thus 

 the two independent lines of evidence unite in indicating that each 

 region of the brain has its own work to do, its own memories to pre- 

 serve. 



While the anatomical evidence in favor of the localization of 

 memories is as strong in the case of man as it is in that of the dog 

 or ape, the physiological evidence is wanting. Physiologists lament 

 that they can not experiment upon man, and psychologists are slow to 

 admit that these experiments throw any light upon man's mind and its 

 action. Just here, however, the study of disease comes in to help out 

 our knowledge. Disease may be regarded as an experiment of Nature 

 to satisfy both physiologists and psychologists, and its results are the 

 more satisfactory, since man is an animal who can describe his sensa- 

 tions during the experiment, as no other animal can. The nature and 

 value of the evidence for the localization of memories to be derived 

 from the study of disease will be clear after the blood-supply of the 

 brain in man is understood. Every artery divides and subdivides as 

 it passes outward from the great central artery of the body — the aorta 

 — so that the vascular system may be likened to a tree, with trunk, 

 boughs, branches, and twigs. Each terminal division of an artery sup- 

 plies with blood a little cone-shaped mass of brain, the base of the cone 

 being the gray surface of the brain, and its apex being the point of 

 entrance of the little artery. In the brain the terminal branches of 

 the arteries do not run into each other, as in some organs, so that each 

 little cone, like the leaf on the tree, is independent of adjacent cones 

 and hangs upon its own arterial twig. Now, it is evident that any- 

 thing which plugs up the artery is going to cut off the blood, and 

 therefore the nutriment from the little cone of brain, and then the lit- 

 tle cone will wither and die. The larger the artery plugged, the greater 

 the surface of brain destroyed. This is the process of disease known 

 as embolism or thrombosis. But such a destruction of brain-tissue 

 in man corresponds to the artificial destruction of brain-tissue in the 

 dogs experimented upon, with this advantage in the case of man, that 

 the shock of the operation is avoided. The experiments of Nature and 

 of the physiologist are therefore parallel. The only difference is in 

 the order of the observation. The physiologist cuts out a definite part 

 and observes the result. The pathologist observes the result of Nature's 

 experiment by watching the symptoms of his patient, and, after the pa- 

 tient's death, he can ascertain the position of the part diseased. Now, 

 if the old theory be true, according to which the brain acts as a whole, 

 and its various parts do not possess distinct mental functions, a limited 

 area of disease in one part may impair the mental powers but will not 

 produce a loss of one function. If, on the contrary, the new theory 



