THE NERVOUS SYSTEM. 113 



fasciculi within the grey-red layer arc, in part, of the same size 

 as those in the fasciculi, — which is the case particularly with 

 those of the thicker white streak, — in part finer. The fibres 

 which proceed from these fasciculi into the superficial white 

 substance, arc also, usually, of greater size, up to 0003'", many 

 of which form loops; there are, however, in this layer together 

 with these, some of the finest fibrils, measuring 00001 ■"'. 

 Notwithstanding all my endeavours, I have been unable to 

 discover anv connection between the nerve-cells and fibres, 

 in the cortical portion of the cerebrum; but the existence of 

 such a connection would appear to me to be nowhere so 

 probable as here, where the nerve-fibres, especially in the pure 

 grey layer, assume so much the appearance of processes of the 

 cells, as almost to deceive the observer, and where, in any case, 

 they terminate. There are in this situation an immeuse 

 number of nerve-fibres, so fine and pale that they could scarcely 

 be regarded as such, were they not straighter than the pro- 

 cesses, and did they not, particularly when treated with soda, 

 exhibit minute varicosities. If anywhere in the central organs, 

 an origination of nerve-fibres exists here, although it is quite 

 intelligible that it should not yet have been observed, when we 

 consider the delicacy of the structures concerned. 



The corpus callosum presents, in the anterior portions of its 

 body above the septum pellucidum, the fornix, and the corpora 

 striata, dull grey streaks, scattered in the white substance, in 

 which the microscope discovers no cells, but only clear vesicles 

 of 0-003 — 0004'" with nuclei, in the midst of numerous 

 nerve-tubes, similar to what are met with in certain fasciculi 

 of fibres of the corpus striatum. Besides this, Valentin 

 ('Nervenl.,' p. 244) occasionally noticed on the surface of the 

 corpus callosum, between the raphe and the stria obtecta, a 

 delicate grey investment with clear nerve-cells, which appears 

 to be identical with the fasciola cinerea, which is con- 

 tinued into the fascia dent at a of the pes hippocampi major 

 (vid. Arnold. ' Bernerk/ p. 87) ; otherwise the corpus callosum 

 is wholly composed of white medullary substance with parallel 

 nerve-fibres of exactly the same aspect and diameter as those of 

 the medullary substance of the hemispheres. The same may be 

 said, also, of the commissura anterior and fornix, which latter, 

 however, comes in contact with grey substance in very many 



