ON DISTRIBUTION OF THE CELLS IN THE INTERMEDIO-LATERAL TRACT. 107 



them, or are their equivalents, is a somewhat insecure foundation on which to rest the 

 statement that the cells of the lateral horn are present in a region where there is no 

 other evidence of them beyond cells in the lateral reticular formation." 



Sherrington has not been able to trace lateral horn cells higher than the middle of 

 the superficial origin of the eighth cervical nerve. In Rhesus he has not found them 

 above the surface origin of the first thoracic root. The lower extremity of the tract 

 he finds to correspond to the surface origin of the fourth lumbar nerve. This would 

 correspond to the third lumbar segment in man. As regards the longitudinal distribu- 

 tion or grouping of the cells in the intermedio-lateral tract, Waldeyer notes, on p. 19, 

 that they lie close together, and that they may be arranged in groups or clusters 

 separated by interspaces in which there are no cells. " Bezuglich ihrer Anordnung ist 

 zu sagen dass sie gewohnlich dicht zusammengedrangt liegen. Selbst wenn keine 

 grossere Zahl dieser Zellen vorhanden ist liegen sie haufig zu zweien, dreien oder vieren 

 nahe beisammen ; zwischen diesen einzelnen kleinen Gruppen konnen dann allerdings 

 grossere Zwischenraume vorhanden sein. Jedenfalls bilden diese Zellen stets eine 

 besondere Formation im Rlickenmarke." 



This arrangement of the cells in groups or clusters has also been referred to by 

 Ainslie Hollis, in the Journal of Anatomy and Physiology, vol. xvii., 1883, p. 63 : 

 ; ' The (intermedio-lateral) tract consists of clusters of small (mostly pyriform) cells 

 arranged linearly, and dissociated from each other, and from the column of sparsely 

 scattered giant cells to which they are contiguous, by a delicate fibrillar stroma of 

 synectic tissue. In the mid-dorsal region I have observed two adjacent columns of 

 these cell-clusters." Again, at p. 520, referring to " the vesicular columns of Clarke 

 and the tractus intermedio-lateralis," he says that " in certain parts of the cord they 

 are found closely congregated in cell-nests." 



Mott (Brain, 1890, p. 444) says: "The cells of the intermedio-lateral tract are 

 found throughout the dorsal region. The cells are bi-polar, and in vertical sections 

 they are often seen to exist as little groups or nests of vesicular cells, from eight to 

 twelve in number." 



Onuf and Collins (Sympathetic Nervous System, 1900, p. 140), in describing the 

 cells of the lateral horn, say : " The group is represented by a very pure type in the 

 lower dorsal region. In longitudinal sections it does not appear in the form of a 

 continuous column, but segmented, in the form of cell-nests distributed at intervals." 



Argutinsky, a pupil of Waldeyer's, in a valuable paper in vol. xlviii. of the Archiv 

 fur mikroskopische Anatomie (1897), " Ueber eine regelmassige G-liederung in der 

 grauen Substanz des JRiickenmarks beim Neugeborenen und uber die Mittelzellen," 

 in which he for the first time describes a segmentation of the " Mittelzellen " of 

 Waldeyer, refers, on p. 514, to a somewhat similar mode of grouping of the cells of the 

 intermedio-lateral tract. He says : " Verfolgt man die Seitenhornzellsaule in einer 

 Serie von Sagittallangsschnitten, vom Seitenstrang zur Mittellinie vorschreitend, so 

 sieht man, wenn man dem Seitenhorn sich nahert, erst eine oder ein paar Langsreihen 



