650 PHYSIOLOGY OF THE CEREBRUM 



the region of the motor areas; clonic inspiratory spasm (snuffing) by stimula- 

 tion of the border of the olfactory bulb and tract, also on the uncinate gyrus. 



Bechterew and Mislawsky make mention of a vasoconstriction from stimu- 

 lating certain parts of the motor region, and a vasodilatation from other parts. 1 



From these observations it may be gathered that the cerebral cortex, espe- 

 cially the motor zone and its immediate neighborhood, exercises an unmis- 

 takable influence on the vegetative processes of the body. 



Doubtless this influence is greater over some organs than over others. 

 Movements like those of the larynx and to a certain extent also those of the 

 thorax, which can be very exactly and very delicately graduated, especially after 

 long practice, must naturally be very intimately dependent upon the cerebral 

 cortex, even though the coarser movements of the same anatomical parts, such 

 as are necessary for the mere ventilation of the lungs, are independent of 

 the cerebrum. Quite different effects have been obtained from the cerebral 

 cortex on the heart, blood vessels, etc. These effects, as has been repeatedly 

 observed, are most correctly regarded as reflexes similar to those which are 

 discharged by all kinds of afferent nerves. Most of them are accessory to the 

 muscular movements controlled by the cortex, and some at least, like the 

 acceleration of the heart and vasoconstriction, accompany every voluntary 

 movement. The chief significance of this cortical influence on the circu- 

 latory organs is that they can be thereby adapted to the different requirements 

 placed upon them. The effects of psychical states on the vegetative functions 

 of the body, which have been discussed at page 577, are in all probability 

 mediated by the cerebral cortex. 



Finally, there are certain observations which indicate that different por- 

 tions of the cerebrum have a different influence on the general state of nutri- 

 tion of the body. Thus, if a large part of the most anterior portion of the 

 dog's cerebrum be extirpated on both sides, the animal always exhibits a 

 tendency to become lean and to remain so; he suffers very extensively also 

 from a persistent inflammatory skin disease which is associated with great 

 redness and itching. On the other hand, a dog deprived of its occipital lobe 

 on both sides regularly becomes fat. It sometimes happens in this case that 

 the dog acquires an eczema also, but it is much more easily held in check 

 and much more easily cured (Goltz). 



3. THE SENSORY CORTICAL AREAS 



The first method which we naturally think of in attempting to determine the 

 significance of the cerebral cortex for sensation, is the investigation of effects 

 upon the different sensations in man and animals which result from lesion, 

 destruction or extirpation of different portions of the cortex. In experiments 

 on animals, however, we meet at once with an obstacle in the fact that we 

 can only judge of the probable loss of sensation by the movements and general 

 behavior of the animal. Our conclusions are therefore very uncertain, espe- 

 cially in cases where the intelligence of the animal is greatly reduced. Since 

 it is just such cases which ought to be most decisive for the purpose in hand, 



1 For the effects of the cerebral cortex on the digestive organs, see pages 261, 264, 284. 



