SENSE AREAS AND ASSOCIATION AREAS. 231 



accompanying diagram (Fig. 102) . So far as the motor regions are 

 concerned, there is some evidence that the connection thus es- 

 tablished is between symmetrical parts of the cortex (Muratoff), 

 that is, between parts having similar functions, and we may 

 regard the corpus as a means by which the functional activities 

 of the two sides of the cerebrum are associated. On the human 

 side, study of cases of lesions of the corpus callosum has yielded an 

 important suggestion in line with the conclusion just stated. 

 Liepmann* has reported cases of this kind in which there were 

 apraxic symptoms (dyspraxia) in the movements of the left side 

 of the body, although the right cortex was uninjured. He draws 

 the conclusion that in movement complexes in general the left 

 hemisphere leads or initiates, as in the case of articulate speech, 

 and that through the commissural fibers of the corpus callosum 

 a stimulus is conveyed to the right cortex when the movement 

 affects the musculature of the left side. 



The Corpora Striata and Thalami. The numerous masses 

 of gray matter found in the cerebrum beneath the cortex, 

 in the thalamencephalon, and in the midbrain have each, of 

 course, specific functions, but, in general, it may be said that 

 they are intercalated on the afferent or efferent paths to or from 

 the cortex. Their physiology is included, therefore, in the 

 description of the functions mediated by these paths. For 

 instance, the lateral geniculate bodies form part of the optic 

 path. In addition, however, these masses of cells contain 

 in many cases reflex arcs of a more or less complicated kind, 

 through which afferent impulses are converted into efferent 

 impulses that affect the musculature or the glandular tissues 

 of the body. The large nuclei constituting the corpora striata 

 (nucleus caudatus and n. lenticularis) and the thalami have 

 been frequently studied experimentally to ascertain whether 

 they have specific functions independently of their rela- 

 tions to the cortex. These efforts have given uncertain results. 

 Older experiments (Nothnagel), in which the attempt was made to 

 destroy these nuclei by the localized injection of chromic acid, are 

 probably unreliable, as the destruction involved also the protection 

 fibers passing to the cortex. Lesions of the nucleus caudatus are said 

 to be accompanied always by a rise in body temperature md an 

 increase in heat production, and stimulation of the same nucleus 

 gives a very marked rise in blood-pressure. These facts indicate 

 a possible connection of this nucleus with heat and vasomotor 

 regulation. Other observers have supposed that these nuclei are 

 especially concerned in the co-ordination of the muscles employed 

 in involuntary or unconscious movements. While the nucleus 

 * Liepmann, "Med. Klin.," 1907, 725. 



