5 88 THE NERVOUS SYSTEM 



Corpora Striata. The corpora striata are situated in front and to 

 the outside of the thalami, partly within and partly without the lateral 

 ventricles. 



Each corpus striatum consists of two parts: An intraventricular portion, 

 the caudate nucleus, which is conical in shape, with the base of the cone for- 

 ward (this consists chiefly of gray matter), and an extraventricular portion, 

 the lenticular nucleus, separated from the other portion by the internal cap- 

 sule. The lenticular nucleus is shown in a horizontal section of the hemi- 

 sphere to consist of three parts, the two internal called globus pallidus major 

 and minor, and the outer called the putamen. 



The cells of the corpora striata are somewhat evenly distributed, and not 

 grouped in nuclei. Their axones pass for the most part into the internal 

 capsule. It is doubtful if these ganglia have any direct anatomical relations 

 with the cortex of the brain, but they are intimately connected by fibers to and 

 from the thalami, and are connected with the substantia nigra (Flechsig). 

 These nuclei are developed from the walls of the embryonic brain tube and 

 are probably therefore homologous with the areas of the cortex. Their lesion 

 is said to be accompanied by disturbance in muscular co-ordination. Lesion 

 of the left lenticular nucleus is said to cause some disturbance in the power of 

 speech, though this has not been observed in the case of the right nucleus. 

 Lesions of the corpora striata produce disturbances in heat regulation, 

 causing a rise of body temperature, the rise amounting to as much as 2 or 3 

 C. in the rabbit. The rise of temperature in man after lesion of the corpus 

 striatum on one side is said to be chiefly on the opposite side of the body 

 (Kaiser). 



VI. THE CEREBRUM. 



That portion of the brain which is concerned with all intellectual functions 

 is the cerebrum or, more strictly speaking, the cerebral cortex. The cerebral 

 cortex is the seat of those activities which we describe as intelligence 

 including states of consciousness, acts of idea formation and volition, and 

 the phenomenon of memory. 



The cerebrum includes the cerebral cortex, the mass of fibers connecting 

 it with lower portions of the brain, the basal nuclei represented by the 

 corpora striata, the thalami, etc. The structure and function of these 

 basal nuclei have already been given briefly, so we may turn our attention 

 now to the cerebral cortex. 



Structure of the Cerebral Cortex. The cerebral cortex forms a large 

 part of the mass of the cerebrum, in fact of the whole brain. Its superficial 

 appearance presents a series of ridges and folds, the gyri and sulci. For gen- 

 eral convenience anatomists have divided the cerebral cortex into five lobes: 

 the frontal, that portion in front of the fissure of Rolando extending down 



