454 REPORT — 1900. 



running outwards from the main central portion. The significance of 

 these figures is probably as follows : F. H. Scott ^ has shown that the 

 jSTissl's substance is a nucleo-proteid, which .amongst reptiles remains 

 throughout life intranucle.ar, Ijut which in other vertebrates is found out- 

 side the nucleus. T.aking these facts into consideration, we .ai'e led to con- 

 clude that the crescent is a specially modified part of the nuclear membiune 

 through which normally the nucleo-proteid is passed out into the body of 

 the nerve-cell. Tliat similar nucleo-proteids do pass out in ordinary 

 epithelial cells has been ascertained in inflammatory conditions of the 

 epidermis,- and in gland-cells generally.'^ 



On comparing epithelial witli nerve cells we find in both a system of 

 fibrils which runs right through the cell ; secondly, material secreted by the 

 nucleus and occupying a position Ijetween the fibrils, and lastly a system of 

 intracellular lymph channels (Holmgren). During the last year the existence 

 of these channels in the nerve-cells of the spinal, sympathetic, and central 

 nervous systems of the rabbit, cat, and monkey has been confirmed by using 

 erythrosin instead of eosin in conjunction with toluidin-blue. Holmgren 

 holds that these canals serve to carry a free supply of lymph to the nerve- 

 cell, while Mann suggests that they are tubes which carry away from the 

 cells and towards the fields of conjunction ensymes for tlie elaboration of 

 the lymph, so as to make the latter directly assimilable by the cell 

 processes. Nissl's bodies, then, are zymogen granules secreted by the 

 nucleus, stored up during rest, and discharged during activity.' 



Golgi's intracellular network in sj)inal ganglia and the anterior horn 

 cells of the spinal cord may he demonstrated by fixing tissue in '2}j per 

 cent, potassium iodide saturated with iodine, and then taking them through 

 aceton into }3arafiin. The network seems in the spinal ganglia to form a 

 framework on which Nissl's substance is deposited. The latter is removed 

 by the potassium iodide, while the framework remains. 



Other points Avhich the serial sections have brought out are : — 



1. The mesencephalic (so-called descending) root of the fifth nerve 

 arises from cells which are quite distinct from the cells of the Lociis 

 coer^ilens. Their axis cylinders have very distinct nodes of Ranvier. 



2. The sensory decussation, as shown in the fillet, is only a more pro- 

 nounced condition of a general arrangement, holding good for the whole 

 length of the cord, the decussating fibres being derived from a small- 

 celled nuclevis situated on a level with, and lateral to, the central canal. 

 The afferent fibres to it correspond to Pal's dorsal bundle. The two nuclei 

 are connected by a commissure of very fine meduUated nerve-fibres run- 

 ning dorsally to the well known anterior white commissure. 



.3. Stilling's sacral and cervical nuclei, Clarke's dorsal column, Blu- 

 menau's nucleus, Deiter's nucleus, and the cells of the mesencephalic root 

 of the fifth nerve seem to belong to the same system, which lies dorso- 

 laterally, and is characterised by large cells. The nucleus above referred 

 to under No. 2, the gracile and cuneate nuclei proper, the mesial trian- 

 gular nucleus of the eighth nerve, and the Loons coernhvs form a dorso- 

 mesial system containing small cells. 



' Trans. Canadian Institute, 1898-99. 



- Mann, Histolofiy of Vaccinia, L.G.R., 1899. ' Trambusti, Galeotti, Hnio. 



'' The intracellular IjTnpli channels are well shown in the electrical nerve-cell of 

 Malapterurus. The structure of this cell was displayed at the Liverpool meeting of 

 the British Association b^ Mann's charts, &c. (1895). 



