Elements of animal physiology, chiefly human . various functions of the ner- If^ ANIMAL PHYSIOLOGY. vous system constitutes that of innervation, and consistsin the generation and transmission of motei imjoulses(sec. 149), of sensation, and of thought, volition, andemotion. Eor every act of innervation—that is, forevery idea thought, every emotion excited, every sensa-tion felt, brain tissue is burnt or 390. Sensation is the process by which we Lecomeconscious through the brain of impressions received andtransmitted to it by the afierent or sensory nerves (). When sensation is
Elements of animal physiology, chiefly human . various functions of the ner- If^ ANIMAL PHYSIOLOGY. vous system constitutes that of innervation, and consistsin the generation and transmission of motei imjoulses(sec. 149), of sensation, and of thought, volition, andemotion. Eor every act of innervation—that is, forevery idea thought, every emotion excited, every sensa-tion felt, brain tissue is burnt or 390. Sensation is the process by which we Lecomeconscious through the brain of impressions received andtransmitted to it by the afierent or sensory nerves (). When sensation is excited normally—that is,by external agency—it is termed objective sensation;but when it arises without any external cause, that is,is produced by the unprompted or rather intrinsic actionof the brain or nervous system itself—it is termed sub-jective sensation, as in the case of the ringing in theears sensation with which most are more or less requires— Anterior Lobe. Corpus Callosum. Middle Lobe. Posterior Nerves??^ from Spi nlCunl. Fig. 81. Side View of Human Brain, showing Cerebral Lobes .andCranial Nerves (of Right Hemisphere), Cerebellum, Medulla Ob-longata, and Corpus Callosum. The observer is supposed to be lr,o1<ingat the right side of the great Lonjihuliiial Fissure,anJthe cut portion o£ t]io Coiyui Valloium, FUNCTIONS OF THE CEREBRUM. 173 (1.) A suitable medium for recejvmr/the external impression orstimulus—as tlie to receive light. (2.) A means of transmitting the impression to the brain—asthe optic nerve. (3.) Brain organization to develop consciousness of impression. 391. The Brain or Encephalon.—The principal partsof the brain are the cei^ehrum or brain proper, the cere-helium or lesser brain, the j^ons Varolii and the unedullaohlongata. It also contains a series of ganglia at itsbase—viz., the corpora striata, optic thalami separatedfrom each other by the third ventricle, corpora quadri-gemina, the pi
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