804 THE BASAL GANGLIA OF THE CEREBRUM. 



partial origin of the optic nerve, it probably bears some relation to the 

 sensation of vision. In man injury of the posterior third may give rise 

 to visual disturbances. Removal of the optic thalamus or destruction 

 of the parts in the neighborhood of the inspiratory center in the wall of 

 the third ventricle impairs coordinated movement in rabbits. Also in 

 man, contralateral disorders of coordination, choreiform twitchings or 

 ataxia have been observed to follow degeneration of the optic thalamus. 

 Destruction of the optic thalamus gives rise in man to loss of mimetic 

 expression on the opposite side of the face in response to emotional 

 influences, although the muscles can be moved voluntarily. 



Bechterew concludes as a result of experiments and of pathological observa- 

 tions that the optic thalami play an important part with respect to the expression 

 of varied perceptions, sensations, and emotional activities. They are motor 

 centers through the intermediation of which principally the congenital movements 

 of expression (such as laughing or crying) are executed, and which are excited 

 under the influence of involuntary psychical impulses, such as emotions, or they 

 can be stimulated reflexly through tactile stimulation and irritation of other 

 sensory organs. The thalamus and the anterior quadri geminate body contain 

 the centers for complex reflexes. Both receive connections from the posterior 

 nerve-roots of the spinal cord and from the sensory cerebral nerves, and the 

 thalamus, in addition, from the olfactory and optic tracts. The anterior quadri- 

 geminate body contains a common optico-auditory reflex path. The optic thal- 

 amus contains also the reflex center for the secretion of tears and from this situa- 

 tion the sensory irritation is conveyed to the path for the secretory branches of 

 the trigeminus and the facial, as well as of the sympathetic. 



After injury of one thalamus paresis or paralysis of the contralateral muscles, 

 together with circular movements, have been reported in some cases, and contra- 

 lateral hemianesthesia with or without involvement of the motor sphere in other 

 cases. Fibers pass from the thalamus to the cortex of all of the cerebral lobes, 

 also to the cornu Ammonis and the tegmentum of the cerebral peduncle, 

 Extirpation of certain portions of the cerebral cortex in the rabbit is followed by 

 atrophy of certain portions of the thalamus. The relations of the optic thalamus 

 to reflex inhibition are discussed on page 731, to the movements of the stomach 

 on page 288, to those of the intestines on page 791. The heat-center supposed to be 

 situated in the thalamus is described on page 395. 



Injury of the cerebral peduncles gives rise, first of all, to severe pains 

 and spasms on the opposite side of the body, where the salivary glands 

 secrete. These irritative phenomena are followed, as paralytic symp- 

 toms, in man by contralateral anesthesia and loss of voluntary control 

 of the muscles as well as paralysis of the vasomotors. In case of lesions 

 of the peduncles in man the oculomotor nerve should be observed, as it 

 is often paralyzed on the same side. 



The middle third of the cerebral peduncle comprises the well-known conduct- 

 ing path of the pyramidal tracts. The fibers of the inner third connect the frontal 

 lobe through the superior cerebellar peduncle with the cerebellum. The outer 

 third contains fibers that connect the pons with the temporal and occipital lobes 

 of the cerebrum. The fibers passing from the tegmentum into the corona radiata 

 serve for sensory conduction. 



According to Goltz section of the cerebral peduncle in the dog is followed 

 by a tendency to fall to the same side; the movements of the contralateral ex- 

 tremities appear larger and cutaneous sensibility is impaired on the entire contra- 

 lateral side. The animal sees especially only objects that make an impression 

 upon the right half of each retina. Therefore, each peduncle, according to Goltz, 

 contains motor and sensory fibers for the entire body. 



Irritation or section of the pons gives rise to pain and spasm. After 

 section of the contained conducting fibers sensory, motor, and vasomotor 

 paralyses appear, together with forced movements. An explanation is 



