THE CEREBELLUM, MEDULLA AND MIDBRAIN 167 



smooth muscles and glands. The sympathetic system is, there- 

 fore, the system through which these processes have their nervous 

 control. In the paragraph dealing with the medulla the exist- 

 ence therein of reflex " centers " for the various " vital " processes 

 was mentioned. On the afferent side these centers are subject to 

 all sensory stimulations which affect the Body. On the efferent 

 side they act through the sympathetic system. 



This reflex mechanism is not subject to voluntary control ex- 

 cept for the single case of the muscle of accommodation of the 

 eye, the ciliary muscle. This muscle is innervated through the 

 sympathetic system, but can be voluntarily controlled as com- 

 pletely as any muscle in the Body. When we say that the sym- 

 pathetic system is not under voluntary control we are simply 

 stating in other words that the motor area of the cerebrum is not 

 able to establish connection through the pyramidal tracts with 

 the neurons of the sympathetic system. Since this system is 

 outside the control of the motor area all reflexes which affect it 

 must be immediate ones. Only present stimuli can arouse it to 

 activity. When we bear in mind that the proper functioning of 

 the Body requires its vital activities to be adjusted to its im- 

 mediate circumstances and not to its circumstances of a week or 

 a year ago, the necessity that sympathetic reflexes be immediate 

 ones is manifest. 



The Relation of the Sympathetic System to Emotional States. 

 A curious feature of the Body's functioning is the way in which 

 emotional states affect the sympathetic system. Nearly all of the 

 well-recognized reactions which the Body makes under emotional 

 stress are reactions of smooth muscles or glands. Blushing and 

 pallor result from changes in the smooth muscles of the blood- 

 vessels; the hair stands on end under the influence of fright, an 

 effect of smooth muscles in the skin; in conditions of embarrass- 

 ment the mouth becomes dry through inhibition of the salivary 

 gland, or the Body is drenched with sweat from stimulation of 

 the sweat glands. 



Although these effects are extremely well marked the mechan- 

 ism by which they are produced is unknown. Their fuller under- 

 standing waits our increased knowledge of the nature of emotion 

 itself. 



A striking feature of emotional reactions is that they do not 



