THE CEREBRUM 163 



man its primary sensory function is lost and it is said to pro- 

 duce an important internal secretion whose physiological value 

 is still obscure. 



The hypothalamus includes the tuber cinereum and mammil- 

 lary bodies (see Figs. 53, 78, and 79), these structures being 

 olfactory centers, and the hypophysis or pituitary body (which 

 has been removed from the specimen shown in Fig. 53, its point 

 of attachment being the infundibulum). The hypophysis is a 

 glandular organ which produces an internal secretion of great 

 importance in maintaining the proper balance of the metabolic 

 activities of the body. The hypothalamus is an important cen- 

 ter for the correlation of olfactory impulses with various visceral 

 functions, including probably the sense of taste. 



The thalamus is in the human brain chiefly a sort of vestibule 

 through which the systems of somatic sensory nervous impulses 

 reach the cerebral cortex. There are, however, two parts of the 

 thalamus which should be clearly distinguished. The ventral 

 part contains chiefly motor coordination centers. It is feebly 

 developed in the human brain, where it is termed the subthala- 

 mus (not to be confused, as is often done, with the hypothala- 

 mus, see Figs. 78, 79, and 81). The dorsal part of the thalamus, 

 in its turn, contains two distinct types of sensory correlation 

 centers: (1) primitive sensory reflex centers, chiefly in the medial 

 group of thalamic nuclei ; (2) the more lateral nuclei which form 

 the cortical vestibule to which reference was made above. 

 These lateral nuclei are sometimes called the new thalamus 

 (neothalamus) in distinction from all of the other thalamic 

 nuclei which form the old thalamus (palseothalamus). 



The centers which comprise the new thalamus make up by far 

 the larger part of the thalamus in the human brain and include 

 the following nuclei: the lateral, ventral, and posterior nuclei 

 (for general cutaneous and deep sensibility) receiving the 

 spinal, trigeminal, and medial lemnisci; the lateral geniculate 

 body and pulvinar (visual sensibility) receiving the optic tracts; 

 the medial geniculate body (auditory sensibility) receiving the 

 lateral or acoustic lemniscus. The lateral and medial genicu- 

 late bodies comprise the metathalamus of the B. N. A. (see p. 

 121 and Fig. 50, p. 118), which in this work are described as 

 part of the thalamus. 



