THE NERVOUS SYSTEM 549 



which tR'ere is perhaps the most general agreement are the vari- 

 ous sensory (afferent projection) areas already enumerated (p. 545) 

 and the motor (efferent projection) precentral area (Fig. 365). These 

 areas myeHnate first (at or soon after birth), next areas adjacent to 

 them, and last areas occupying a considerable portion of the human 

 pallium but much less extensive in other mammals. There is 

 much difference of opinion as to the extent to which these last 

 myehnating areas are suppHed with projection fibres. According 

 to some authorities the areas myelinating last have no projection 

 fibres and are consequently entirely composed of association cells 

 and fibres. Perhaps the two best-marked of the various areas are 

 the motor and visual areas the structure of which is shown in figures 

 362, 363 and 364. The motor precentral cortex is characterized by 

 the presence of the giant cells of Betz, by an almost complete absence 

 of an internal granular layer and by a great wealth of fibres. The 

 calcarine or visual area is characterized by a strongly marked line 

 of Gennari ( = Baillarger) and by a double or triple internal granular 

 layer containing large granules in place, apparently, of the superficial 

 large pyramids. The line of Gennari is probably partly composed 

 of the terminals of the fibres of the optic path (geniculo-calcarine 

 fibres). 



TECHNIC 



(i) The general structure of the cerebellum is well brought out by staining 

 sections of formalin-MuIIer's fluid-fixed material with haematoxylin-picro-acid- 

 fuchsin (technic 3, p. 21), and mounting in balsam. 



(2) The arrangement of the cell layers of both cerebellum and cerebrum as 

 well as certain details of internal structure of the cells, can be studied in sections 

 of alcohol- or formalin-fixed material staihed by the method of Nissl (technic, 



P- 39)- 



(3) The distribution of the medullated nerve fibres of either the cerebellar or 

 cerebral cortex is best demonstrated by fixing material in Miiller's fluid (technic 

 4, p. 6) or in formalin-Miiller's fluid, and staining rather thick sections by the 

 Weigert or Weigert-Pal method (technic, p. 34). 



(4) The external morphology of the cerebellar and cerebral neurones and the 

 relations of cell and fibre can be thoroughly understood only by means of sec- 

 tions stained by one of the Golgi methods (technic, pp. 36 and 37). Especially 

 in the case of the cerebellum, sections should be made both at right angles, and 

 longitudinal to the long axis of the convolution. Golgi preparations from 

 embryonic material and from the brains of lower animals furnish instructive 

 pictures. 



(5) The silver method of Cajal should be used, especially with alcohol fixa- 



^ 



