OAPSULA INTERNA, COEPUS STEIATUM, INTEEBEAIN-GANGLIA. 263 



ing from the stria medullaris externa and particularly from the Tentral 

 nucleus, may be traced as far as the end of the oblongata, perhaps into the 

 lateral columns of the spinal cord also. The stria medullaris interna is not 

 traceable beyond the midbrain. From the most posterior thalamic region 

 arises the radiatio thalami ventralis, the termination of which is entirely 

 unknown (oblongata — lateral columns of cord). 



On the accompanying very diagrammatic illustration (Fig. 168) is to be 

 studied the relation of the thalamus to the base of the brain, to the central 

 ventricular gray matter, to the capsula interna, and to the nucleus lenti- 

 formis. 



You will observe something in this section that until now could merely 

 be mentioned cursorily. It is the region internal to the lenticular nucleus 

 and ventral to the thalamus. There are collected here several fiber-strands, 

 running somewhat parallel with one another, which, in part, cross the in- 

 ferior portion of the capsula interna at an angle, in part pass on over it. 

 Those fibers which are superior belong to the lenticular fiber-system; they 

 form the ansa lentiformis, previously mentioned. The inferior fibers are 

 the coronal fibers to the thalamus, which come from the occipital and tem- 

 poral lobes; they are designated as the inferior pedicle of the thalamus 

 (u. s., Fig. 159). The entire mass. of fibers met with in section in Fig. 168 

 ventral to the nucleus lentiformis is called the substantia innominata. 

 Just behind the substantia innominata the fibers of the capsule, which be- 

 come the pes pedunculi, or crusta, emerge at the base of the brain. The 

 substantia innominata bounds the crus cerebri at the anterior end. It re- 

 sembles a loop laid over the peduncle in front, and is therefore designated 

 as the ansa peduncularis. 



The diagram (Fig. 159), moreover, departs so far from the real appear- 

 ance that it will be advantageous to give some attention to the opposite 

 illustration of an actual section through the thalamus of a dog (Fig. 169). 



From this and the following illustrations you will obtain a better idea of the 

 structure of the interbrain than I could give you heretofore. They contain 

 somewhat more details (pedicles of the thalamic nuclei, etc.) than were mentioned 

 in the text, because they are intended to afford an opportunity to study actual sec- 

 tions more closely. I beg to make use of these illustrations again at the end of this 

 and the next chapter. 



In the preceding two chapters it was necessary to describe so many 

 brain-structures by themselves that I fear I can hardly have succeeded in 

 giving you a correct idea of the relation of these parts as a whole and to one 

 another. Such a conception must be thoroughly acquired, however, because 

 even a better knowledge than I have been able to give you of the fiber- 

 systems and ganglia will be of little value when you come to study a brain 

 topographically. The time has arrived, then, when I must demonstrate to 



