( 17 ) 



loo lioniogeneoiis. A loss of* cells docs iiol seem to have (aken place here. 

 Rabbit W. 11. 26th. Oct. 1909. 



Sagittal division of the frontal thii-<l of the corpus callosum. The 

 animal, after awakening from the narcose, showed no other abnor- 

 mality than a very insufficient, and often totally absent, eye-lid 

 reflex on sudden li.oht. 



It was killed on November 9th. 1909. Besides the intended lesion 

 the right thalamus opticus in its dorsal part is slightly injured. The 

 left half of the cerebrum is quite uninjured, and stained with 

 toluidiue blue after paraffine imbedding; the right one was examined 

 by Marchi's method. The latter does not furnish any important data 

 on the subject dealt with. The blackened granules of the degenerated 

 myeline sheaths are very fine, and not to be traced with sufficient 

 certainty beyond the deepest coi'tex layers. 



The cortex of the rodentia shows several features very different 

 from those of carnivorous animals. Through the whole neopallium 

 at least the half of all the nerve cells are of a vesicular character, 

 even in the regions where the lamination is quite clear. These more 

 or less round cells have a large, bright nucleus, with a deejily 

 stained nucleolus, and very little protoplasm. They fill out almost 

 completely the 2nd.^), 4th., and 6th. layers. The so-called giganto- 

 pyramidal cells of Brodmann's area 4 (motor zone) are not confined 

 to the fifth layer, but intermingle with the more superficial layers; 

 a distinct lamina granularis interna cannot be spoken of, as has 

 been pointed out by Brodmann. The right corner of fig. 6 shows the 

 condition described ; the photo is taken from a transverse section in 

 the most frontal level where the corpus callosum fibres pass from 

 foto 7, 8, 9. right to left (see diagram 6a). Imme- 



diately on the lateral border of the 

 most distal point of the giganto- 

 pyramidal zone a cortex field appears, 

 which shows the six typical layers 

 in a very characteristic way. The 

 difference mentioned between the 

 constituents of the 2nd., 4th., and 

 broad 6th. layers on the one side, 

 and those of the 3rd. and 5th. on 

 the other, is obvious. 



A part of the same section is 

 Fig. 6a. represented in figure 7 more highly 



magnified. The photogram has been cut immediately beneath lamina V. 



^) Where it is present. 



2 

 Proceedings Royal Acad. Amsterdam. Vol. XIV. 



ill in. ant. 



