MODEL OF MEDULLATED TRACTS IN BABY's BRAIN 125 



mus, and the cortex, and between the lateral surface of the globus 

 pallidus (no. 27) and the cortex. These two bundles make up the 

 cortical radiation medullated in the specimen (no. 28). The gap 

 between the lemniscus and the cortical bundle is best seen in fig. 

 4, the lemniscus being numbered 18, and the thalamo-cortical 

 bundle, 26. For the globus pallidus, the fibres to the medial part 

 are seen as 19 in fig. 4, while the cortical radiation no. 28 is far to 

 the side and seen best in fig. 11. 



The medullated part of the cortical radiation needs special de- 

 scription. It consists, as has just been said, of two parts, one from 

 the lateral zone of the thalamus (no. 26, figs. 4 and 11), the other 

 from the lateral part of the globus pallidus (no. 27, fig. 11). 

 Beyond the border of the thalamus as seen in fig. 4, these two 

 bundles are absolutely indistinguishable, and the fused mass 

 makes the cortical radiation labeled no. 28 in all the figures. The 

 thalamic part of the radiation is the less extensive at birth. It 

 is shown best in fig. 4 as no. 26. Here it will be seen to be a curved 

 bundle in the form of a figure 6. The caudal part which, from the 

 point of view of the cerebrum proper, is the ventral part, curves 

 around the lateral nucleus of the thalamus ; the stem of the 6 lies 

 in the external medullated lamina of the thalamus, which gradually 

 joins and fuses with the general cortical radiation. In sections 

 this thalamo-cortical bundle which is medullated at birth is well 

 illustrated in the literature, in the new-born, by Barker^^ in his 

 fig. 664 This section is from one of our series and shows the thal- 

 amic radiation labeled Th, in its positon just cerebralward to 

 the lateral geniculate body The same figure shows the globus 

 pallidus w^ith its capsule of fibres which makes the lenticular part 

 of the cortical radiation. In this series the cortical radiation ex- 

 tends both to the anterior as well as to the posterior central con- 

 volution while in the one from which the model is made, has only 

 the posterior central bundle medullated. In the adult, the first 

 thalamo-cortical bundle to be medullated is illustrated by Dejerine^^ 

 in his second volume (page 310, fig. 282). The caudal curved 

 part of the bundle (see fig. 4), which represents the fibres emerging 



1^ Barker, The Nervous System. New York, D. Appleton & Company, 1899. 

 First edition, page 1051, fig. 664. 

 " Dejerine, ibid. 



