Royal Mieroseopical Society, 5 



At the sides of the convohition, a part of the fibrillae, originating 

 in the network of the grey layer, take another course, by making 

 before leaving the grey layer a turn toward the base of the convo- 

 lution ; then they enter the nucleated layer, and, after being 

 converted into dark-bordered nerve fibres, run along its border 

 around the bottom of the sulcus, to pass over into the neighbouring 

 convolution. These fibres connect, therefore, the grey layer of two 

 convolutions. Nevertheless, other fibres, leaving the grey layer 

 around the bottom of the sulcus, are also observed, which cross 

 those connecting fibres obliquely and pass through the nucleated 

 layer into the white substance. 



The ganglionic bodies of PurJcinje are found, as we know, near 

 the inner border of the grey layer ; many of them project even 

 with a part of their body into the nucleated layer; their basal 

 process belongs therefore to the latter. When we meet with this 

 process entirely isolated, it is generally partly torn ofi", and there- 

 fore seldom longer than 3V t^^^- Nevertheless, I saw it pass into 

 a dark-bordered nerve fibre, which I was able to pursue, while 

 passing along between the nuclei, to a considerable distance, and in 

 a dh'ection toward the white substance. Its diameter near its origin 

 is 3^0 mm., diminishing at a distance of about ^V ^^^' from the 

 body to 6 iTo mm. 



The dark-bordered nerve fibres, issuing from the nucleated 

 layer, form the white substance. The transition from the former 

 to the latter, however, is only gradual, and it is therefore diffi- 

 cult to draw a distinct limit between them. The difiiculty consists 

 in the extension into the white substance, not only of the nuclei, 

 lying now farther distant from each other, but also of the granular 

 substance, which here still appears in the form of small isolated 

 groups of granules, though without terminal network. The fine 

 fibrinous neuroglia, extending itself between the nerve fibres, from 

 the white substance below upward, contributes also to lend to the 

 whole structure a confused appearance. As far as I have been 

 able to ascertain, there exists no communication between the indi- 

 vidual nerve fibres of the white substance of a group or leaf of 

 convolutions of the cerebellum.* In examining these fibres in a 

 thin section, or in a fine bundle, split ofi" from the white substance 

 at a point where they leave a group of convolutions, a considerable 

 difi'erence is found to exist in their diameter. While this, namely, 

 measures in the greater number of fibres from ^hs to ^^o mm., 

 others are met with of only -^^ mm., and, again, some even as thick 

 as 2^0 mm. We might venture to presume, therefore, that while the 

 larger nerve fibres of the white substance be a continuation of the 

 hasal process of the ganglionic bodies of PurMnje, the axis cyhn- 



* The above description relates to the long convolutions of the hemispheres 

 of the cerebellum of man. 



