THE NERVOUS SYSTEM. 435 



which expands in it, forming numerous white fasciculi. The 

 grey substance presents, as almost universally, nerve-cells and 

 fine nerve-fibres. The former, "which measure from (VOOC — 

 O018'", are, in part, colourless, and in part, contain pigment, as, 

 especially, in the caudate nucleus and third segment of the 

 lenticular nucleus; they are furnished with from two to five 

 processes, and occur in greater numbers according to the depth 

 of colour of the grey substance. 



The nerve-fibres may be referred for the most part to those 

 of the basis of the crura cerebri. They present the form of 

 dark-bordered tubes from 0*0012 — 0005'", most of them from 

 0-002 — 0-004"' in size, which, running parallel and close 

 together in a straight direction, enter the first division of the 

 lenticular nucleus, and the most anterior, thickest portion of 

 the caudate nucleus. When traced further in the lenticular 

 nucleus, it will be seen that they form larger and smaller 

 fasciculi, decreasing somewhat in size (most of them measuring 

 from 0"0012 — 0-003'"; and that, passing straight through the 

 more scanty grey substance of the first divisions of the 

 lenticular nucleus, they are all ultimately lost, spreading out 

 in a penicillar form in its outermost and largest division. 

 That is to say, white fasciculi measuring from 004 — 014"', 

 with fibres of 0*0012 — 0'002'", enter this division of the 

 nucleus from the second ; and these fasciculi in close con- 

 tiguity, slightly diverging and subdividing into smaller bundles, 

 are continued further in a direction towards the outer border 

 of the lenticular nucleus, before reaching which they disappear 

 to the naked eye. If traced microscopically in preparations 

 made with chromic acid, it is apparent, that the fasciculi 

 proceed nearly to the outermost part of the lenticular nucleus, 

 though gradually broken up into smaller bundles and separate 

 fibres, and most intricately interlaced with each other. That 

 these fibres terminate here, and do not proceed any further into 

 the medullary substance of the hemispheres, may be considered as 

 made out, not the faintest indication of any further continuation 

 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 grcjit 



