Microscopic Studies on the Central A'ervous 

 .--A System of Reptiles and Batrachiaiis. 



By John J. Mason, M. D. 



ARTICLE 11. niAIVIKTKKS OF THK NUCLKI OF NKRVK OKr-F-S IN 'IHE 



Sl'INAL ('OKI). KANA; KMYS FLORTDANA ; TKS- 

 TLnn) I'OLYPIIiaiUS. 



{Reprliitiif from The JorRNAL of Nervous and Mental Disease, .lull/, ISSO.t 



A S earh' as 1875, while studying tlie histology of the frog's 

 -^--*- spinal cord, with special reference to the effect pro- 

 duced by poisons, I was often impressed by what ap))eared 

 to be an inequality between the size of the nerve-cells in the 

 brachial and those of the crural enlargement. This differ- 

 ence was most striking in longitudinal sections, where a long 

 column of cells was under observation. They appeai'ed to be 

 larger in the crural than in the bracliial region. The idea of 

 ascertaining by actual measurement whether the inequality of 

 size were real or apparent, was not then entertained, because 

 it seemed to me that measurements of the body of the cell 

 must be unsatisfactory, owing to the great and constant diver- 

 sity in its form and in the number, size, and length of its 

 prolongations or processes. Later I was led to measure the 

 nuclei, and last winter published in the January number of 

 this journal the fact that there is a considerable ditt'erence in 

 the frog between the two enlargements of the spinal cord, as 

 to the diameters of the cell-nuclei. 



Neither Tieissner, Stieda, nor an_y other anatomist, had, up 

 to this time, given in their writings comparative uieasiire- 

 ments of nuclei taken from these two regions of the cord. 

 Whatever shapes the cell-body may assume, or whatever may 

 be the nature of its substance, the nucleus in these animals 

 presents itself to us always as a sharply-defined, persistent 

 anatomical element, easily prepared for microscopical exam- 

 ination. Tieadilv colored l)v carmine, \\i both fresh and hard- 



