THE FUNCTIONS OF THE CEREBRUM. 269 



it becomes to perform the operation and to keep the animal alive. 

 In higher animals, such as monkeys, however, life is impossible 

 without the cerebrum, thus supporting the conclusion, which we 

 have already drawn (see p. 243), that the cerebrum comes to 

 be a necessary part of every reflex action in the higher animals. 



Cerebral Localization. The various functions of the cere- 

 brum are located in different portions of it. This localization 

 of cerebral functions has been very extensively studied during 

 recent years, partly by experimental work on the higher mam- 

 malia and partly by clinical studies on man. Careful observa- 

 tions are made of the behavior of the various functions of the 

 animal either after removal or destruction of a portion of the 

 cerebrum, or during its stimulation by the electric current. Im- 

 portant additions to our knowledge of cerebral localization are 

 also being made by correlating the symptoms observed in insane 

 persons with the lesions which . are revealed by post-mortem 

 examination. 



It has been found that there are roughly three areas on the 

 cerebrum with distinct and separate functions (Fig. 50). 



I. In the portions of the cerebrum which lie in front of the 

 ascending frontal convolutions prcfrontal region are located 

 the centers of the intellect (thought, ideation, memory, etc.). 

 This part of the cerebrum is accordingly by far the best de- 

 veloped in man; it is much less so in the apes and monkeys, 

 becomes insignificant in the dog, and still more so in the rabbit. 

 It has been destroyed by accident in man with the result that 

 all the higher mental powers vanished. 



II. The next portion includes roughly the region of the 

 cerebrum bordering upon the Rolandic fissure (i. e., the ascend- 

 ing frontal and ascending parietal convolutions). Here are 

 located the highest centers for the movements of the various 

 parts of the body. Microscopic examination of the grey matter 

 reveals the presence of large triangular nerve cells, which com- 

 municate by synapses (see p. 241) with the afferent fibers that 

 carry the sensory impulses, whose course from the posterior 

 spinal roots we have already traced (p. 246). From each of 

 these cells an efferent fiber runs to join the pyramidal tract 



