MODEL OF MEDULLATED TRACTS IN BABY's BRAIN 115 



light on two points, first, the form relations of the medial lem- 

 niscus and the fibres of the red nucleus in their relations to the 

 thalamus, and secondly, on the form of the internal capsule in 

 relation to the thalamus and corpus striatum, notwithstanding 

 the fact that much of the internal capsule is non-medullated. 



The model is shown in a series of five drawings, three from the 

 mesial aspect and two from the lateral. Fig. 1 represents a 

 mesial view of the entire model and fig. 9 a lateral view. The 

 other figures, namely, 3, 4 and 1 1 , represent dissections of the model 

 to show the various structures. The nuclei are represented in a 

 solid tone, the non-medullated bundles are faintly streaked, while 

 the medullated bundles have a blue tone. Fig. 2 is a drawing 

 of the mesial aspect of a baby's brain, given for the purpose of 

 orienting the first three figures of the model, while fig. 10 is a view 

 of a dissection of the pyramidal tract given to orient the lateral 

 views of the model. Both figs. 2 and 10 are from a baby's brains 

 of which, however, we have no records of the age. It is ob- 

 viously older than the one from which the model was made, in 

 which the pyramidal tract is not at all medullated. Four figures 

 of sections are given, two from the baby's brain from which the 

 model was made, and two taken at about the same level from an 

 adult brain. 



In the description of the model I shall follow this plan. First, 

 I shall take up the medullated tracts beginning with the lem- 

 niscus medialis and the group of tracts associated with it. The 

 various nuclei will be mentioned in connection with the fibre 

 bundles. Secondly will follow a description of the form of the 

 internal capsule, both the non-medullated and the medullated 

 part, and thirdly, an account will be given of the nuclei of the 

 thalmus, hypothalamus and corpus striatum, with the associated 

 medullated bundles. The following table gives a list of all the 

 medullated tracts found in the series in approximately the order 

 in which they are taken up. 



