FUNCTIONS OF THE CEREBRUM. 695 



and appreciate them as sensations ; that impressions may be here connected and give 

 rise to various of the phenomena of animal and intellectual existence ; that impressions 

 are recorded by the memory ; and, finally, that certain parts are endowed with special 

 functions. But beyond this, psychology is a science mainly of introspective observation, 

 the facts contributed by the experimentalist being few and barren. The observer of intel- 

 lectual phenomena studies the process of development of the mind ; he soon separates 

 the instinctive phenomena, observed in the lower animals and in the human being with- 

 out experience, from the acts which follow experience, observation, the recording of im- 

 pressions by memory, and the generation of ideas ; he brings his perfected intelligence 

 to bear upon the process of development of the same kind of intelligence in the human 

 being progressing from infancy to adult life ; and, finally, the psychological philosopher 

 attempts, by introspective observation, to study the workings of the perfect intellect, his 

 only means of investigation being the very intelligence he is endeavoring to comprehend. 



At the present day, we are in possession of a sufficient number of positive facts to 

 render it certain that there is and can be no intelligence without brain-substance ; that, 

 when brain-substance exists in a normal condition, intellectual phenomena are manifested, 

 with a vigor proportionate to the amount of matter existing ; that destruction of brain- 

 substance produces loss of intellectual power ; and, finally, that exercise of the intellect- 

 ual faculties involves a physiological destruction of nervous substance, necessitating 

 regeneration by nutrition, here, as in other tissues in the living organism. The brain is 

 not, strictly speaking, the organ of the mind, for this statement would imply that the 

 mind exists as a force, independently of the brain ; but the mind is produced by the 

 brain- substance ; and intellectual force, if we may term the intellect a force, can be pro- 

 duced only by the transmutation of a certain amount of matter. In view of these facts, 

 which have long been more or less fully recognized, though not, perhaps, very accurate- 

 ly defined in words until within a few years, it is not surprising that attempts have been 

 made to locate the different mental attributes in particular portions of the brain. The 

 pseudo-science of phrenology is the most marked example of such an attempt; but this 

 has so slight a basis in fact, that it does not, at the present day, merit serious scientific 

 discussion. 



In treating of the functions of the cerebrum, we shall not discuss psychology, except 

 in so far as physiologists have been able to connect the mind, taken as a whole, with a 

 distinct division of the nervous system. In this we shall draw upon experiments on liv- 

 ing animals, facts in comparative physiology, in pathology, and, to a certain extent, the 

 relations clearly shown to exist between the development of intelligence and certain of 

 the nerve-centres, in different races of men and different individuals. With regard to 

 the location of particular functions in distinct portions of the cerebrum, we have but 

 little definite knowledge, beyond the experiments already cited in treating of the irrita- 

 bility of the cerebral substance, and the probable location of the faculty of speech. The 

 latter point will be fully discussed in its appropriate place. 



Extirpation of the Cerebrum in the lower Animals. It is, perhaps, sufficiently evident, 

 from anthropological and pathological observations as well as the study of comparative 

 physiology, that the intellectual faculties reside in the encephalon ; but these methods of 

 investigation do not clearly indicate the special functions of different parts of the cranial 

 contents. We have seen, in our general sketch of the anatomy of the brain, that this is 

 by no means a simple organ, and that certain parts, although they are bound together by 

 commissural fibres, have sufficient anatomical distinctness to lead the physiologist to sup- 

 pose that they may have separate and peculiar properties and functions. One of the 

 most valuable methods of investigation of the functions of these separate ganglia is that 

 of extirpation of one or more, leaving the others, as far as possible, intact. This method 

 was first employed with marked success by Flourens and has since been adopted by 

 numerous experimenters. It must be remembered, however, that there is no subject of 



