126 FLORENCE R. SARIN 



from the nucleus, Dejerine describes as the triangular zone of 

 Wernicke (see page 357). 



The medullated cortical radiation occupies the postertior limb 

 of the internal capsule, and the models bring out certain funda- 

 mental points about the internal capsule which can be made clear 

 from three figures, namely, 4, 9 and 11. To begin with fig. 4, the 

 internal capsule consists of, two segments, the anterior limb no. 

 31, entirely non-medullated at birth, and the posterior limb, no. 

 28, partially medullated at birth. These two sheets of fibres, the 

 anterior and posterior limbs, stand at an angle to one another; the 

 anterior limb is at a slight angle to the median sagittal plane of 

 the brain proper as can be readily seen in figs. 4 and 1 1 . This point 

 would of course be seen better in a view of the model taken from 

 the dorsal surface of the cerebrum, but it is a point well-known 

 in the adult. The entire posterior limb on the other hand in the 

 brain at birth is in a plane exactly parallel to the median sagittal 

 plane of the cerebrum and hence is a perfectly flat sheet in figs. 4 

 and 11. The anterior limb radiates out betw^een the caudate 

 nucleus and the lenticular nucleus. In fig. 4, if the eye follows 

 the crus or cerebral peduncle (no. 24) forward, it will be seen that 

 it spreads out into a sheet of non-medullated fibres between the 

 lenticular nucleus and the thalamus. This sheet of non-medul- 

 lated fibres which lies in the primitive groove between the dien- 

 cephalon and the telecephalon is the knee of the internal capsule 

 and contains the non-medullated pyramidal tract. The posterior 

 limb of the internal capsule extends between the knee of the internal 

 capsule (no. 36) and the tail of the caudate nucleus (no. 32), as it 

 curves around into the roof of the lateral ventricle. These limits 

 are shown best in fig. 9. This point can be readily related to the 

 adult brain in any dissection of the ventricles, for the knee is 

 determined by the foramen of Monroe and the tail of the caudate 

 is readily seen. 



The zone in which the posterior limb of the internal capsule 

 reaches the cortex is an especially interesting point. Since the 

 posterior limb is a perfectly flat sheet in the model in a plane ex- 

 actly parallel to the median sagittal plane, it reaches the cortex 

 in the upper third of the central convolutions. Thus in a trans- 



