FUNCTIONS OF THE MEDULLA OBLONGATA. 105 



with certain gangliform bodies, which have also their proper func- 

 tions. These are the corpora striata^ the optic thalamic and the 

 tubercula quadrigemina. The corpora striata, and the optic tha- 

 lamic whilst both extensively connected with the cerebral hemis- 

 pheres, are, in the most marked way, connected inferiorly with 

 separate and distinct portions of the medulla oblongata ; the corpora 

 striata, with the inferior planes of the crura cerebri, and their con- 

 tinuations, the anterior pyramids, and the optic thalami with the 

 olivary columns, the central and probably fundamental portions of 

 the medulla oblongata. Thus along the tract that passes from the 

 anterior pyramids to the corpora striata, we have none but motor 

 nerves : whilst along the tract that connects the olivary columns 

 with the thalami, there are none but sensory nerves. The thalami 

 then may be regarded as the ganglionic centres of common sensa- 

 tion, standing in the same relation to the sensory nerves, converging 

 from the various parts of the body to the encephalon, as do the optic 

 and other ganglia to their nerves of special sensation. On the other 

 hand, the corpora striata are implanted on the motor tracts of the 

 crura cerebri, which descend into the anterior pyramidal columns ; 

 and their connexion with the motor function is very generally ad- 

 mitted, from the constancy with which paralysis is observed to ac- 

 company lesions of these bodies. 



According to the views above expressed, the corpora striata and 

 optic thalami bear to each other a relation analogous to that of the 

 anterior to the posterior horn of the spinal gray matter. The cor- 

 pora striata and anterior horns are centres of motion ; the optic 

 thalami and posterior horns, centres of sensation. 



The tubercida quadrigemina are the true optic ganglia, the ence- 

 phalic recipients of the impressions necessary to vision, which, ac- 

 cording to Bowman, are doubtless simultaneously felt by means of 

 the optic thalami; they are also the centres of those movements of 

 the iris which contribute largely not only to protect the retina, but 

 likewise to increase the perfection of vision. Irritation of an optic 

 tubercle on one side causes contraction of both irides. 



This is quite in accordance with the fact, that if light be admitted 

 to one eye so as to cause contraction of its pupil, the other pupil will 

 contract at the same time. Whatever other functions the tubercula 

 quadragemina may perform, they have a sufficiently obvious relation 

 to the optic nerves, the eye, and the sense of vision. They may 

 therefore be justly reckoned as special ganglia of vision. 



At the base of the brain are found other ganglionic masses, which 

 are in direct connexion with the nerves of sensation, and appear to 

 have functions quite independent of those of the other components 

 of the encephalon. Anteriorly are found the olfactive gangha, in 

 what are commonly termed the btdbous expansions of the olfactory 

 nerve. That these are real ganglia is proved by their structure, 



