704 THE CEREBRUM 



and medulla oblongata. In addition, its pulvinar prominences, to- 

 gether with the lateral geniculates and anterior corpora, form the end- 

 station of the primary division of the optic tract, while the median 

 geniculates and posterior corpora receive the auditory tract. It is 

 also connected with the cerebellum, and sends a few fibers to the red 

 nucleus and medulla oblongata. l 



In accordance with its connections with the cutaneous, sensory, 

 optic and auditory tracts, Monakow 2 regards the thalamus opticus, 

 together with the lateral and median geniculates, as a subsidiary cere- 

 bral cortex, the purpose of which is to transfer these sensations to the 

 proper association areas. Lesions of this body, therefore, must give 

 rise to very diverse symptoms. This also holds true of the outgoing 

 impulses. Bechterew, 3 for example, calls attention to the loss of the 

 emotional movements concerned with laughing and crying, and the im- 

 pairment of the mimic play of the facial muscles. This investigator 

 also states that this body contains the reflex center for the secretion of 

 the tears. Its activation also produces a dilatation of the pupils, a 

 bulging of the eyeballs and a retraction of the eyelids. Injury to this 

 body also gives rise to the so-called phenomenon of Romberg, i.e., 

 to an inability to stand erect when the eyes are closed. This symptom 

 serves as a diagnostic sign in tabes dorsalis and other degenerative 

 affections of the nervous system. 4 



THE CORPORA QUADRIGEMINA 



The anterior corpora receive a part of the optic fibers and direct 

 them to the cortex of the occipital lobes. The posterior corpora, to- 

 gether with the median geniculates, serve as end-stations of the second- 

 ary auditory fibers, and communicate with the cortex of the temporal 

 lobes and other parts of the cerebrum. In the lower forms, the destruc- 

 tion of these bodies occasions blindness in both eyes, while their 

 unilateral laceration gives rise to blindness either in the corresponding 

 eye or in that of the opposite side. This diversity in the effects is caused 

 by differences in the crossing of the optic fibers. In the monkeys and 

 man, blindness does not result, 5 for the reason that the loss of these 

 relay stations is compensated for by a transfer of their optic impulses to 

 other tracts. 



The anterior corpora contain the center for the constriction of the 

 pupils, the impulses being transferred in this place from the optic tract 

 to that of the oculomotor. Furthermore, this transfer is distinctly 

 reciprocal, because the stimuli brought to bear upon the retina of one 



1 Wallenberg, Neurol. Zentralblatt, xx, 1901, 50. 



2 Gehirnpathologie, Wien, 1904. 



3 Neurol. Zentralblatt, x, 1894, 481. 



4 Wilbrand and Sanger, Die Neurologie des Auges, Wiesbaden, 1904; also 

 Sachs, Brain,, i, 1909. 



6 Deutsche Zeitschr. fur Nervenheilkunde, xvii, 1900, 428. 



