Pathological Anatomy, too, has been extremely unprofitable. "The results of Pathological Anatomy (says Muller) can, however, never have more than a limited application to the physiology of the brain. We are unacquainted with the laws according to which the different parts of the organ participate in the functions of each other, and we can only, in a general way, regard as certain that organic diseases in one part of the brain may induce changes in the function of other parts; but from these facts and the results of Pathological Anatomy, we cannot always draw certain conclusions." Mr. Solly, after commenting on the general failure of Vivisection, remarks, "From pathology we might naturally expect surer evidence; but even here the physiologist who carefully examines its records is doomed to disappointment. As will be proved hereafter, no certain light has yet shone on physiology from this source." Cerebral pathology will not continue to be so barren a study when we have a true cerebral physiology to guide us. I find all pathological cases instructive as confirmations and illustrations of true cerebral science.
The method of Dr. Gall--studying the growth and development of the different parts of the brain, as indicated by the cranium--is the most simple, rational and successful of all the methods adopted up to the present time. In his hands it has elicited a valuable and practical, though rude, system of phrenology. But Craniology or skull-study cannot perfect, nor can it positively demonstrate, the science.
The observations of the craniologist are continually liable to error. The irregular thickness of the skull constitutes a great difficulty in the way of exact observations. By great expertness and accuracy of observation, he may overcome this difficulty in a great degree, but whenever the brain is subject to any remarkable influence, increasing or diminishing the activity and size of particular organs, the external form fails to indicate the internal condition, because it can change but slightly, and with slowness, after the skull is fully developed and ossified. Were the skull composed of more pliable materials, cranioscopy would be more accurate in its facts, but while it preserves a uniform exterior, the interior often undergoes remarkable changes. Convolutions that are frequently called into action become better supplied with arterial blood, expand and grow, while the adjacent portion of the inner plate of the skull becomes absorbed, and presents a remarkable indentation. Convolutions that are seldom in action shrink in size, and the adjacent bone grows in upon them. Thus the skull becomes thinner at the site of every active organ, and thicker over every convolution that is inactive. The translucency or opacity of the different parts of the skull, when a light is placed in its interior, generally indicates the active and inactive organs. Hence, many skulls of fine exterior reveal, upon interior examination, a degenerate character. Criminal heads generally present remarkable opacity and thickness in the region of the moral organs, with distinct digital impressions from the convolutions of the lower organs.