MODEL OF MEDULLATED TRACTS IN BABY's BRAIN 117 



line at a point marked 4 in fig. 1. This point is ventral to the cen- 

 tral canal, just caudal to the inferior olive. Within the medulla, 

 the bundle from the nucleus funiculi gracilis is joined by the more 

 diffuse mass of internal arcuate fibres from the nucleus funiculi 

 cuneati (no. 5, fig. 1.) These two crossed tracts make the lem- 

 niscus in the medulla, which is a broad band as seen from the 

 mesial aspect. It lies close to the raphe, hemmed in between the 

 two inferior olives. In the pons, the lemniscus spreads out to 

 the side making a narrow b'and in the mesial plane. In the lower 

 part of the pons can be seen the position of the superior olive (no. 

 7, fig. 3), quite far to the side, and the lateral lemniscus emerging 

 from it. Throughout the pons, the medial and lateral lemnisci 

 are parallel. At the cerebral end of the pons, the lateral lemniscus 

 curves still farther lateralward, and turns dorsalward to enter the 

 nucleus of the inferior colliculus (no. 8, fig. 3). 



The medial lemniscus, on entering the mid-brain shows a num- 

 ber of interesting points. In the first place, it gives off a small 

 bundle which enters the caudal tip of the substantia nigra (no. 9, 

 figs. 3, and 7). In using the term enters, it is not intended to as- 

 sume the direction of the fibres since Weigert sections cannot give 

 the relation to the cell body. Secondly, from the dorsal border 

 of the medial lemniscus is given off the superior lemniscus which 

 curves dorsalward parallel to the lateral lemniscus to enter the 

 superior colUcuhis (no. 10, figs. 3 and 4). Thirdly, the entire mass 

 of the medial lemniscus curves lateralward to make room for the 

 red nucleus. This can be seen in fig. 1, but better in fig. 3, and 

 best in fig. 4, from which the red nucleus has been removed. 

 Lateral to the red nucleus, the lemniscus gives off a small bundle 

 to the nucleus hypothalamicus of Luys, exactly similar to the 

 one given off to the substantia nigra (no. 11, figs. 3, 7, and 8). 



The relations of the lemniscus to the thalamus are complicated. 

 It has been found that the fibres run to two nuclei, namely the 

 center median of Luys, and the ventro-lateral nucleus. Here it 

 may be well to enumerate the nuclei of the thalamus w^hich can 

 be made out and modeled, though they will not be described 

 until later: 



