CER'EBRO-SPINAL MENINGITIS. See ME:N=0ms, ante.
Cerebrum (Lat. the brain) is sometimes applied to the whole contents of the cranium or skull; but more usually it denotes the upper portion, while the under and posterior portion is called the CEREBELLUM, or little brain. In this article we shall briefly notice the chief results which have as yet been obtained regarding the uses of the various parts of the mass, referring to the article BRAIN for the necessary anatomical details.
The crura cerebri appear as the principal conductors of impressions to and from the cerebrum. When one is divided, the animal moves round and round, from the injured towards the sound side, as if from a partial paralysis of the latter side. The effect may be referred to the interruption of the voluntary impulses from the C., for although the cerebellum seems to have the office of combining the muscles, whose co-operation is necessary for each action, the effort of the will must proceed from the cerebrum.
The corpora quadrigemina are, as stated in the article BRAIN, of the optic ganglia of the lower animals." Their removal wholly destroys the power of seeing, and diseases by which they are seriously affected are usually accompanied with blindness. Disease or destruction of one corpus quad. produces blindness of the opposite eye. Prob ably their connection with vision is not their only function.
The optic thalami probably participate slightly in the visual function of the corpora quadrigemina; but we have no definite evidence on this point. They are intimately connected with the power of movement. Destruction of one of them causes rotation of the animal, similarly to division, of one of the crura cerebri. Longet has shown, that after removing all the cerebral hemispheres and the corpora striate, the animal can still stand and walk, but that on removing one of the optic thalami, it falls down paralyzed on the opposite side, or commences rotatory motion.
The function of the corpora striata is very uncertain; they have probably some con nection with sensation and volition, the precise nature of which is at present unknown.
The parts hitherto considered—including the cerebellum—appear to comprise the apparatus (1.) For the direction and government of all the unfelt and involuntary move ments of the parts which they supply; (2.) For the perception of sensations; and (3.) For the direction of such instinctive and habitual movements as do not require the exercise of any reasoning or intellectual act. They cannot be regarded as organs of the higher faculties of the mind.
The functions of the cerebral hemispheres are, in the words of Dr. Kirkes (Handbook, of Physiology), those of organs by which the mind, 1st, perceives those clear and more impressive sensations which it can retain and judge according to; • 2d, performs those acts of will, each of which requires a deliberate, however quick, determination; 3d, retains impressions of sensible things, and reproduces them in subjective sensations and ideas; 4th, manifests itself in its higher and peculiarly human emotions and feelings, and in its faculties of judgment, understanding, memory, reflection, induction, and imagination, and others of the like class.
" The evidences that the cerebral hemispheres are, in the sense and degree indicated above, the organs of the mind, are chiefly these: 1. That any severe injury of them, such as a general concussion, of sudden pressure by apoplexy, may instantly deprive a man of all power of manifesting externally any mental faculty; 2. That in the same general proportion as the higher mental faculties are developed in the vertebrate animals, and in man at different ages, the more is the size of the cerebral hemispheres developed in comparison with the rest of the cerebrospinal system; 3. That no other part of the nervous system bears a corresponding proportion to the development of the mental faculties; 4. That congenital and other morbid defects of the cerebral hemispheres are, in general, accompanied with corresponding deficiency in the range or power of the intellectual faculties and the higher instincts." See Mirth, THE HUMAN.