344 



ANATOMY OF THE CENTEAL NEBVOUS SYSTEM. 



also (the latter running in the forniz). Others of the tracts of the corona 

 radiata, however^ do not go to the thalamus, but pass on farther downward, 

 in front of, to the outside of, and back of it, to terminate in centers that 

 lie deeper. 



The corona radiata is therefore composed of fibers that go to the thala- 

 mus and of fibers that go to deeper lying parts. 



1. Fibers pass to the thalamus from almost the entire surface of the 

 cortex, and by no means so few bundles as the diagram before you would 

 indicate. These fibers unite, in part, close to the thalamus to form thicker 

 bundles, which are called the pedicles of the thalamus. 



Monakow has been able to show, by means of numerous cases of second- 

 ary degeneration, that a very definite cortical zone sends its fibers to each 

 of the thalamic nuclei. We shall have occasion to consider these in more 

 detail later on. At present we will mention only some of the most important 



Fig. 159. — Diagram of the fibers of the corona radiata, especially the fibers to the 

 thalamus. TJ. S., Inferior pedicle; Sehhiigel, Thalamus. 



tracts of this groiip, known as the tradus cortico-thalamici. First, there is 

 the cortical tract of the fillet. It arises from the region posterior to the 

 anterior central gyrus and terminates in the most ventral thalamic nuclei. 

 The fibers of the fillet also pass thither from the spinal cord and medulla 

 oblongata. For this reason, we may regard the tract mentioned as the con- 

 tinuation of a considerable part of the sensory radiation to the cortex. In 

 the posterior region of the thalamus there lies a part of the primary termina- 

 tions of the optic nerve. The afl:erent tracts from the cortex to these are 

 also well known. They pass forward, after leaving the medulla of the 

 occipital lobe, in an almost horizontal direction, and end in the groups of 

 ganglia of the posterior region of the thalamus. In Fig. 160 this "optic 



