534 TEXT-BOOK OF PHYSIOLOGY. 



groups which are centers for reflex actions in connection with ocular move- 

 ments: e.g., closure of the lids, contraction of the sphincter pupillae, con- 

 vergence of the eyes, etc. 



The Corpora Quadrigemina. From the anatomic relation of the 

 superior quadrigeminal body (the pre-geminum) to the optic tract, the 

 inference can be drawn that it is in some way essential to the performance of 

 various reflex ocular movements and perhaps to the variations in size of the 

 pupil. Experimental investigations and pathologic changes support the 

 inference. 



Irritation of the pre-geminum in monkeys on one side is followed by 

 diminution of the pupils first on the opposite side and then almost immedi- 

 ately on the same side. The eyes at the same time are also widely opened and 

 the eyeballs turned upward and to the opposite side. If the irritation be 

 continued, motor reactions are exhibited in various parts of the body. 

 Destruction of the pre-geminum in both monkeys and rabbits is followed by 

 blindness, dilatation and immobility of the pupils, with marked disturbance 

 of equilibrium and locomotion (Ferrier). 



From the anatomic relation of the inferior quadrigeminal body (the 

 post-geminum) to the lateral fillet, the basal tract for hearing, the inference 

 may be drawn that it is in some way connected with the auditory process. 



Stimulation of the post-geminum gives rise to cries and various forms 

 of vocalization. Pathologic states of this body are also attended by impair- 

 ment of hearing and disorders of the equilibrium. 



From the foregoing facts it is probable that the corpora quadrigemina are 

 associated with station and locomotion. Ferrier assumes that in these 

 bodies "sensory impressions, retinal and others, are coordinated with adap- 

 tive motor reactions such as are involved in equilibration and locomotion." 



The Corpora Striata. The relation of these bodies to the pyramidal 

 motor tract would indicate that they are in some way connected with motor 

 activities. Their function, however, is obscure. While stimulation of one 

 corpus produces convulsion of the muscles of the opposite side of the body,, 

 and destruction gives rise to paralysis of the corresponding muscles, it is 

 difficult, owing to the intimate association of the white and the gray matter, 

 to state to which the phenomena are to be attributed. The evidence at 

 hand points to the conclusion that if a lesion is limited to the gray matter the 

 paralysis which might result would be but temporary and of short duration. 

 The pathologic evidence is of a similar character. Gowers is of the opinion, 

 that if the lesion is small and at a sufficient distance from the white fibers of 

 the capsule, there may even be no initial hemiplegia; neither motor nor 

 sensory paralysis will arise if the lesion is confined to the gray matter. 



It is stated by some experimenters that localized injuries, both experi- 

 mental and pathologic, are followed by a persistent rise of temperature, 

 varying from i to 2.6 C. 



The Optic Thalami. From the anatomic relation of the optic thalami 

 to the general and special sense nerve-tracts, on the one hand, and to the 

 cerebral cortex, on the other hand, it is assumed that they are connected 

 with the production of sensations both general and special, and act as 

 intermediaries between the peripheral sense-organs and the cortex. 



The results of experimental stimulation and destruction of the thalami 



