THE NERVOUS SYSTEM. 383 



into smaller bundles and separate fibres, and most intricately interlaced 

 ■with each other. That these fibres terminate here, and do not i^roceed 

 any further into the medullary substance of the hemispheres, may be 

 considered as made out, not the faintest indication of any further con- 

 tinuation being afforded, which, if it existed, could not escape being 

 seen : on the other hand it is doubtful how they terminate here. All 

 I have to state on the point is this : that the fibres of the nerve-fasciculi, 

 entering the third division of the lenticular nucleus, as may be directly 

 observed in a very great many instances, gradually become so much 

 attenuated, as ultimately to measure not more than 0-0008, 0*0006, or 

 even hardly 0*0004 of a line, and present an almost entirely pale aspect, 

 so that they can scarcely any longer be distinguished from the finer 

 processes of the nerve-cells ; with which in fact, unless everything is 

 deceptive, they most probably are actually connected. All the fibres, 

 also, which enter the caudate nucleus, present exactly the same condi- 

 tions ; some of these enter the nucleus directly from the basis of the 

 cerebral peduncle, others, which appear in its thinner portion, are 

 manifestly derived from the lenticular nucleus, the first two divisions of 

 which they traverse in the first instance ; in this case, also, there is no 

 transition of the fibres into the medullary substance of the hemispheres, 

 but a separation of the fasciculi into a plexus of the finest, almost non- 

 medullated fibres takes place, and probably a connection between them 

 and the cells. 



Besides the above described, in any case very numerous, nerve-fibres 

 derived from the cerebral peduncles and terminating in the corpora 

 striata, the nuclei of those bodies contain a considerable number of 

 other fibres, whose origin it is, in part, difiicult, and, in part, impossi- 

 ble to assign. I think I can trace one set of these fibres to their 

 source. In the most external part of the large nucleus of the corpus 

 striatum, we find, on making various sections, a considerable number of 

 moderately strong fasciculi, though not visible to the naked eye, which 

 in their relative thickness and the diameter of their tubes (0-0012-0-002 

 of a line) differ from the fibres derived from the crus cerebri, which in 

 this situation are reduced to the most extreme attenuation and dispersed 

 in a plexiform manner. It is easily seen that all these fasciculi proceed 

 from the medullary substance of the hemispheres ; and, as it appears, 

 after they have run a certain distance parallel with the surface on the 

 border of the nucleus of the corpus striatum, that they enter it. Many 

 of these fibres are continued directly from the medullary substance 

 into the ganglia, and, in this way, decussate, at right angles, with the 

 former fibres. Assembled in fasciculi, these fibres penetrate more or 

 less deeply into the gray substance of the corpus striatum, and of the 

 third division of the lenticular nucleus ; and these terminate, as I think 

 I have observed, without any considerable expansion, the formation of 



