MODEL OF MEDULLATED TRACTS IN BABy's BRAIN 121 



nucleus." By comparing the three views of the model from the 

 mesial aspect it will be noted that this forked bundle of the lem- 

 niscus enters the medial part and the caudal surface of the ventro- 

 lateral nucleus. In fig. 1 is shown the rather thin medial nucleus, 

 especially thin along the ventral border. This has been removed 

 from figs. 3 and 4, showing the large lateral nucleus. The size 

 is better estimated in fig. 4, from which the lateral nucleus itself 

 has been entireh' removed. A form relation of the medial lemnis- 

 cus can be especially well seen in figs. 9 and 11, namely, that the 

 medial lemniscus, throughout the superior colliculus region, lies 

 close to the lateral surface in the groove between the crus and the 

 colliculi, but the bundle being straight, it does not enter the ex- 

 treme lateral part of the thalamus which projects so far to the 

 side of the mid-brain. 



The brain at birth then shows that the medial lemniscus, as 

 far as it is medullated, enters two nuclei in the thalamus, the center 

 median of Luys and the cup-shaped nucleus considered as one 

 and the medial part of the ventro-lateral nucleus as the the other. 

 Moreover, in connection with the ventro-lateral nucleus, the med- 

 ullated bundle forms a part of the external medullated lamina. 

 These relations will be clear by comparing figs. 7 and 8. 



The relations of the more ventral part of Forel's Feld H, namely, 

 his fasciculus H2, are especially well shown in the model. The 

 bundle (no. 19, and its continuation, no. 20), appears to arise in 

 the red nucleus. It emerges from the red nucleus, at its cerebral 

 end, close to the mid-line, and, as is seen in figs. 3 and 4, takes 

 the following course; it passes forward dorsal to the the nucleus 

 hypothalamicus of Luys to a point just cerebralward to Luys' 

 body, where it curves sharply ventralward, along the medial 

 border of the crus, and then turns first caudalward and then direct- 

 rectly lateralward along the caudal surface of the first part of the 

 globus pallidus. Within the globus pallidus this bundle is per- 

 fectly sharp in sagittal sections of the adult brain as can be seen 

 by comparing no. 20 in figs. 7 and 8. It lies on the caudal surface 

 of the globus pallidus, adjacent to the optic nerve. This bundle 

 was described by Forel as H^, and is called by Dejerine^ Le fais- 



^ Dejcrine, ibid., vol. 2, page 327. 



