108 DR ALEXANDER BRUCE 



von einzelnen Zellen, wie Perlschniire, zwischen den Liingsfasern des Seitenstrangs 

 ano-eordnet. Dann werden diese einzellio-en Reihen zahlreicher. . . . Die einzelnen 

 Glieder der Seitenhornzellsliulen sind zwar grosser, als die Mittelzellengruppen, doch sind 

 die A.bstande zwischen den Centren zweier Gruppen sowohl bei den SeitenhornzelleD, 

 wie den Mittelzellen gleich so dass beide Zellsaulen Ketten bilden, welche gleich viele 

 und gleiche gelagerte Glieder besitzen." A first perusal of this paper might leave the 

 impression that the segmentation of the middle cells had been confounded with that of 

 the posterior part of the intermedio- lateral tract, but Argutinsky has stated, in a most 

 categorical manner, that the two systems of cells are distinct in form and in position, 

 although he admits that they may approach each other very nearly. An examination 

 of the text of Waldeyer's paper and his plates and diagrams of sections from man and 

 the gorilla shows also that the " Mittelzellen " and the intermedio-lateral tract are two 

 independent systems. Waldeyer has personally confirmed this statement, after 

 examining my preparations. It is evident, therefore, that Argutinsky has noted a 

 segmental grouping of the cells of the intermedio-lateral tract. 



Herring (Journ. Physiol., 1903, p. 285) says : "The cells of the lateral horn vary 

 in size considerably. They occur in groups, and in some sections may be absent from 

 the lateral horn altogether." 



The above references and quotations indicate that several observers had noted the 

 fact that the intermedio-lateral tract is not a continuous column of cells, but that its 

 cells are arranged more or less in groups. So far as I am aware, however, no exhaustive 

 examination has up to the present time been made of the distribution of the cells in the 

 tract. This want it is the object of the present communication to supply. 



In 1903, while engaged in the study, by means of serial sections, of the distribution 

 of the large motor cells and of the smaller and more faintly staining polygonal cells in 

 the cervical enlargement of the spinal cord, I was struck with the appearance in the 

 first dorsal segment, and to a lesser extent in the lower part of the eighth cervical 

 segment, of special groups of cells differing in character and in arrangement from the 

 above-mentioned large motor and small polygonal cells. These groups were situated 

 within or adjacent to the posterior border of the lateral portion of the anterior horn. 

 Under a low power of the microscope they readily attracted the eye, owing to the facts 

 that they were closely grouped together, that they were fusiform in outline, and that 

 their long axes for the most part ran in the same direction. These features, and the fact 

 that they stained almost as deeply as the large motor cells, rendered them exceedingly 

 conspicuous. In the eighth cervical and in the upper part of the first dorsal segments 

 they were found entirely in the white matter either at a little distance from or quite 

 dose to the anterior cornu. In either case they lay behind the junction of the outer 

 and the middle thirds of its posterior border, or behind the outer third. In the lower 

 part of the first dorsal segment this position was departed from, and they gradually 

 encroached forwards upon the grey matter and at the same time passed outwards towards 

 i he lateral margin of the anterior cornu. To speak more accurately, this relative change 



