THALAMI OPTICI, AND CORPORA STRIATA. 



509 



in the Tubercula Quadrigemina, to which the principal part of the 

 roots of the Optic nerve may be traced. Although these bodies are so 

 small in Man, as to be apparently insignificant, yet they are relatively 

 larger, and form a more evidently-important part of the Encephalon, in 

 many of the lower Mammalia ; though still presenting the same general 

 aspect. The Auditory ganglia seldom form distinct lobes or projec- 

 tions ; but are usually lodged in the substance of the Medulla Oblon- 

 gata. Their real character is most evident in certain Fishes, as the 

 Carp ; in which we find the Auditory Nerve having as distinct a gan- 

 glionic centre as the Optic. In higher animals, however, we are able to 

 trace the Auditory nerve into a small mass of gray matter, which lies 

 on each side of the Fourth Ventricle ; and although this is lodged in 

 the midst of parts whose function is altogether different, yet there seems 

 no reason for doubting that it has a character of its own, and that it is 

 really the ganglion of the auditory nerve. We are not able to fix upon 

 any such mass of gray matter, as the distinct G-ustatory ganglion ; nor 



Fig. 155. 



Diagram of the relation of the Sensori-motor tract at the base of the Brain, to the Cerebrum, as seen in 

 horizontal section : olf, olfactive ganglia ; opt, optic ganglia ; and, auditory ganglia ; cs, corpora striata ; 

 thai, thalami optici ; a, a, olfactive nerves ; b, b, optic nerves ; c, c, auditory nerves. 



is it necessary to attempt to do so ; for, as we shall see hereafter, there 

 is strong reason to regard the sense of Taste as only a refined kind of 

 Touch, combined with the sense of Smell. 



901. At the base of the Cerebral Hemispheres, we find two gan- 

 glionic masses on either side ; through which all the fibres pass that 

 connect the Hemispheres with the Medulla Oblongata. These are the 

 Corpora Striata, and Thalami Optici. Upon tracing forwards the 

 tract of motor fibres that ascend from the Anterior Pyramids, we find 

 it passing chiefly into the Corpora Striata; whilst if we follow the 



