706 NERVOUS SYSTEM. 



Taking into consideration all of the pathological facts bearing upon the subject, it 

 seems certain that, in the great majority of persons, the organ or part presiding over 

 the faculty of articulate language is situated at or near the third frontal convolution 

 and the island of Reil in the left anterior lobe of the cerebrum, and mainly in the 

 parts nourished by the middle cerebral artery. In some few instances, the organ seems 

 to be located in the corresponding part upon the right side. It is possible that, origi- 

 nally, both sides preside over speech, and the superiority of the left lobe of the brain 

 over the right and its more constant use by preference in right-handed persons may 

 lead to a gradual abolition of the functions of the right side of the brain, in connection 

 with speech, simply from disuse. This view, however, is hypothetical, but it is rendered 

 probable by certain considerations, among the most important of which is the state- 

 ment by Longet, that " one cerebral hemisphere in a healthy condition may suffice for 

 the exercise of intelligence and the external senses." In support of this statement, 

 Longet cites several cases of serious injury of one hemisphere without impairment of 

 the intellect. In what is called the ataxic form of aphasia, the idea and memory of 

 words remain, and there is simply loss of speech from inability to coordinate the mus- 

 cles concerned in articulate language. Patients affected in this way cannot speak but 

 can write with ease and correctness. In the amnesic form of the disease, the idea and 

 memory of language are lost; patients cannot speak, and are affected with agraphia, or 

 inability to write. In cases in which hemiplegia is marked, the aphasia is usually of the 

 ataxic form ; while, in cases in which there is no hemiplegia, the aphasia is generally 

 amnegic. 



The Cerebellum. 



It is not necessary, in order to comprehend the functions of the cerebellum, as far as 

 these are known, to enter into a full description of its anatomical characters. The 

 points, in this connection, that are most interesting to us as physiologists are the follow- 

 ing : the division of the substance of the cerebellum into gray and white matter ; the 

 connection between the cells and fibres ; the connection of the fibres with the cerebrum, 

 and with the prolongations of the columns of the spinal cord ; and the passage of fibres 

 between the two lateral lobes. These points, therefore, will be the only ones that will 

 engage our attention. 



As we have seen, in treating of the general arrangement of the encephalon, the cere- 

 bellum, situated beneath the posterior lobes of the cerebrum, weighs about 5*2 ounces 

 av. in the male, and 4'T ounces in the female. The proportionate weight to that of the 

 cerebrum is as 1 to 8f in the male, and as 1 to 8J in the female. It is separated from 

 the cerebrum by a strong process of the dura mater, called the tentorium. Like the 

 cerebrum, the cerebellum presents an external layer of gray matter, the interior being 

 formed of white, or fibrous nerve- tissue. The amount of the gray substance is very 

 much increased by numerous fine convolutions and is farther extended by the penetra- 

 tion, from the surface, of arborescent processes of gray matter. Near the centre of each 

 lateral lobe, embedded in the white substance, is an irregularly-dentated mass of cellular 

 matter, called the corpus dentatum. The cerebellar convolutions are more numerous and 

 the gray substance is deeper than in the cerebrum ; and these convolutions are present in 

 many of the inferior animals in which the surface of the cerebrum is smooth. 



The cerebellum consists of two lateral hemispheres, more largely developed in man 

 than in the inferior animals, and a median lobe. The hemispheres are subdivided into 

 smaller lobes, which it is unnecessary to describe. Beneath the cerebellum, bounded in 

 front and below by the medulla oblongata and pons, laterally by the superior peduncles, 

 and superiorly by the cerebellum itself, is a lozenge-shaped cavity, called the fourth ven- 

 tricle. The crura, or peduncles, will be described in connection with the direction of the 

 fibres. 



The structure of the gray substance of the convolutions presents certain peculiarities. 



