ON THE COMPARATIVE HISTOLOGY OF CEREBRAL CORTEX. 453 



Tltp Comparative Hisfolor/i/ of Cerebral Cortex. — Report of the Com- 

 mittee, comisthuj of Professor F. CtOTCH (Chairman), Dr. G. Manx 

 (Secretary), and Professor E. H. Starling. (T)rawii. iip by the 



Secretarij.) 



Since the last report three complete serie.=! of sections have been made of 

 the central nervous system of the bonnet monkey — viz., (1) transverse 

 sections from the thalamus to and including the second dorsal nerve, from 

 material fixed in Mann's picro-corrosive formaldehyde ; (2) a coronal 

 series through the lower part of the medulla and up to and including the 

 eighth cervical segment (fixed in picro-corrosive formaldehyde) ; (3) a 

 Weigert series extending from the fillet decussation to the dorsal cord. 



The reason for investigating these regions was to ascertain whether 

 so-called motor-cells differed from ' sensory ' ones in any definite structural 

 characteristics. Nothing was discovered by which one kind of cell could 

 be distinguished from the other, and it has become evident that Nissl's 

 classification is a purely artificial one. All cells show a distinct fibrilla- 

 tion, and the basophil ' Nissl-substance ' lying between the bundles of 

 fibrils. 



Motor cells, as a rule, have a greater development of the dendra, and, 

 in consequence, the fibrils coming from these processes in coursing through 

 the cell break up the available space in a regular, uniform manner, and 

 hence there results a more regular arrangement of the basophil granules. 

 In sensory cells, on the other hand, because of the special development of 

 one or two dendritic processes one frequently notices on that side of the 

 nucleus looking towards the biggest dendron a pyramidal (in section tri- 

 angular) area, occupied by non-differentiated plasm, and formed by the 

 divergence of the fibrils coming from the big dendron and sweeping round 

 the nucleus. In these cells, as seen most characteristically in the Locus 

 cveruleus, Substantia nigra, lateral horns of the spinal cord and the antero- 

 mesial visceral group of cells, Nissl's granules form relatively coarse aggre- 

 gations towards one side of the cell. At one time it was thought that a 

 certain appearance first described by Mann in 1894 ' in the occipital lobe 

 of the rabbit, since then rediscovered by Roncorini and discredited by 

 Levi — viz., the presence of crescentic bodies on one side of the nucleus — 

 would allow of a ready distinction between nerve-cells in the cerebrum 

 and those found in the lower centres. This, hov/ever, was found not to 

 be the case, for the same appearance is seen throughout the whole length 

 of the spinal cord right down to the coccygeal portion. The examination 

 of the dorsal and lower regions of the cord was made possible through the 

 kindness of Miss M. Purefoy FitzGerald, who placed at our disposal the 

 complete series of sections she is tabulating at Oxford. 



As to the real existence of these ci'escents there cannot be the slightest 

 doubt, for Levi's suggestion that we are dealing with a folding of the 

 nuclear membi'ane is readily disproved by making ti-ansvei'se sections of 

 the cells in the Cornu Ammonis at right angles to their long axis, and 

 staining them by Mann's eosin-toluidin-blue method, when these crescents 

 in question appear one in each nucleus as distinct swellings in the nuclear 

 membrane, while the latter is not stained at all. In addition to the com- 

 mon crescentic type one may frequently see in surface views branches 



1 Jip,irn, Anat.and Plnfsiol. October 1894. 



