MODEL OF MEDULLATED TRACTS IN BABY's BRAIN 129 



well) central convolution. Secondly, a tract having as one element 

 the globus pallidus with cortical radiations reaching the same part 

 of the cortex; the other connections of the globus pallidus bring 

 two different medullated bundles the one relating it to the red 

 nucleus and thus to the cerebellar tracts, the other relating it to 

 the nucleus hypothalamicus of Luj^s, which in turn is connected 

 with the medial lemniscus at birth. 



This completes the description of the bundles medullated at 

 birth, which make a part of the projection system. It will 

 now be necessary, in order to present a complete record of this 

 specimen, to describe the other bundles which are medullated 

 though the model does not, for the most part, show any point 

 in their form relations not shown in the previous model. The 

 first of these tracts is a long tract, namely, the fasciculus longi- 

 tudinalis medialis, whose relations as an optic-auditory reflex 

 path are certainly, in part, brought out by the tracts medullated 

 at birth. The rest of the medullated bundles can be regarded 

 only as fragments of tracts in the present state of our knowledge. 

 The fasciculus longitudinalis medialis (no. 1) is essentially the same 

 in this model as in the first model. That it is a continuation of 

 the ventro-lateral funiculus of the cord can be seen in fig. 1. 

 Almost its entire extent is shown also in fig. 2. In entering the 

 medulla, it curves dorsalward with the central canal, to the floor 

 of the fourth ventricle. Here it shows a slight curve corresponding 

 with the pontal flexture, which is still visible. Within the mid- 

 brain, it forms a deep trough (no. 39, fig. 1), in which lies the 

 nucleus of the oculomotor nerve. Just beyond this trough it is 

 joined by the posterior commissure (no. 40, fig. 1), which decus- 

 sates just dorsal to the aqueduct and joins the fasciculus longi- 

 tudinalis medialis opposite the cerebral end of the red nucleus. 

 The fascicluus longitudinalis medialis curves ventral ward just 

 in front of the red nucleus and comes to an end abruptly. 



The fascilulus retroflexus of Meynert is one of the most con- 

 spicuous of the short tracts medullated early. It is a small com- 

 pact bundle (no. 41), seen only in fig. 1, extending from the region 

 of the ganglion of the habenula of the thalamus into the red 

 nucleus. It could not be traced to a ganglion interpedunculare. 



