352 D. DAVIDSON BLACK 



this account projection fibers of thalamic origin encountered con- 

 siderable mechanical difficulty in gaining the cortex. Many of 

 these fibers failed to reach the cortex and of those that did, the 

 majority come to an end within a short distance of their entrance. 

 These somewhat complicated relations are fully described in the 

 paper cited above. 



The thickened basal portion of the cerebrum representing the 

 cortical area was divided by a Y-shaped median furrow into a 

 median anterior and two lateral posterior regions or lobes. This 

 furrow is not of morphological significance and represents only a 

 mutual form adaptation between the cerebrum and skull base. 

 However, for purposes of description I shall refer to these regions 

 outlined by this furrow as lobes. The relations obtaining in this 

 brain may be seen on reference to figures 1, 2 and 3. In these 

 figures are indicated the approximate areas from which the sec- 

 tions here illustrated were taken. 



The drawings of these sections were all made with the aid of a 

 Leitz projectoscope at a magnification of 130 and are reduced to 

 X 65 in reproduction. This magnification was selected as being 

 the lowest at which even the approximate shape of the smaller 

 cells could be shown. The whole thickness of the inner cortical 

 stratum is not indicated in any of these drawings. 



Technique 



Modified Weigert, modified Nissl and simple hematoxylin and 

 eosin stains were used. The tissue was not in a favorable condi- 

 tion to react to metallic impregnations and although numerous 

 attempts were made, no successful preparations were obtained. 



The approximate distribution of the thalamic fibers, which were 

 the only medulated fibers present in the cortex, was determined 

 by a modified Weigert method. It was found that these fibers 

 when present coursed in general, parallel to the surface of the cor- 

 tex. No typically radial fibers were found. The fibers were 

 poorly medullated and gave to the tissue a peculiar, coarse, reticu- 

 lated character quite different from the almost homogeneous 

 appearance of the fiber laminae of the cortex proper. 



