OF DENISON UNIVERSITY. - -r 



it. The remaining zone of gray is the cortex, and is connected by fibre 

 and cell chains with at least the two median layers. 



In just what way the cortex is related to the optic tract is difficult 

 to determine. In some places there is still a superficial fibre tract 

 corresponding to the stratum zonale. The outer layer of the nates 

 contains, as already said, radiating systems of fibres and cells. Of the 

 latter four kinds are recognized. First, a system of superficial pyra- 

 midal cells, with their bases peripheral, each with a single process 

 passing toward the center. These cells measure .01 7-. 02 mm., with 

 a nucleus .006 mm. in diameter. The protoplasm stains very faintly 

 and the cell gives off a process which may unite with cells of 

 the fourth sort. It must be left at present undetermined whether these 

 cells are really nervous or not. We could not be certain that basal 

 processes connect them with the superficial fibre zone. Second, very 

 numerous nutritive cells of the usual type are scattered irregularly. 

 Third, nucleated cells of the walls of the blood vessels differentiate 

 strongly. Fourth, elongate, bipolar, fusiform cells, .013 mm. long 

 by .003 mm. wide. Below these, and apparently connected with 

 them, are much larger cells of somewhat pyramidal form, with a single 

 peripheral process, blunt proxmial extremity with several processes, and 

 a large nucleus. These cells measure .024-. 02 7 mm. in length by 

 .01-.013 mm. in width. Fig. 6, Plate XIX, is a semi-diagramatic illus- 

 tration of the cells of the superficial layer, as seen in longitudinal sec- 

 tion {Yll-e-2) under the one-fifth inch objective. 



(Consult in this connection Tartuferi^ SuH" Anal. Minut. delT 

 Eminenze Bigem., etc., in Revista Sperimentale, 1879, Ganser, Die 

 periph. u. cent. Anordnung d. Schnervenpaare u. d. Corpus Higem. 

 Ant., Archiv. f. Psychiatric, Bd. XIII., yonakoic, Die Beziehung d. 

 sogenannt. Sehsphaere z. d. infracorticalen Opticu.scentren, etc. ibid, 

 Bd. XIV, and Bellonci, Ueber d. centrale Endigung des Nervus Op- 

 ticus bei d. Vertebraten. Zeitsch. f. w. Zool., Bd. XLVII.) 



At the medio-ventral aspect of the sections which disj)lay the en- 

 trance of the third nerve roots, Meynert's bundle has assumed the 

 longitudinal direction, forming a transversely-cut tract between the 

 roots of which there are over one dozen bundles on either side. In 

 sections farther caudad than Fig. i, Plate IX, the ventricle of the ojuir 

 lobes vanishes without divaricating. The non-api)earance of the col- 

 liculi, as seen in lower vertebrates, is to be explained as due to this 

 fact, /. t'., the substance of the colliculi fused with the sub-natal gray 



