106 DR ALEXANDER BRUCE 



As the present paper concerns itself, however, purely with the tract as it is found in 

 the dorsal, lower cervical, and upper lumbar regions, the question raised in the two 

 previous paragraphs as regards its distribution in the upper cervical and lower sacral 

 regions will not be further referred to. 



The majority of anatomists who have written on the subject since Clarke's original 

 papers appeared have regarded the intermedio-lateral tract as being synonymous with 

 the cells of the lateral horn. This view is not exactly in accordance with the definition 

 or the description and figures of Clarke, an examination of which shows that, as already 

 stated, he was aware that the tract passed beyond the limits of the lateral horn, both 

 backwards along the margin of the grey matter and also inwards towards the column of 

 Clarke {Phil. Trans., 1859, p. 446, PL XX. figs. 2 and 4 ; also PL XXI. figs. 3, 5 and 6). 



Waldeyer, in his work on the Spinal Cord of the Gorilla (Abth. der Konig. Akad. 

 derWissenschaft, Berlin, 1898), has subjected the intermedio-lateral tract to a careful 

 examination, and has done more than any other writer since Clarke to advance our 

 knowledge and broaden our views with regard to the character and distribution of 

 its cells. He makes it clear that the cells of the tract are not limited to the lateral horn, 

 but that also at the margin of the grey matter near the formatio reticularis there are 

 found cells identical with those in the lateral horn. These are, in his opinion, therefore, 

 component parts of the intermedio-lateral tract. He is further of opinion that the 

 tract does not, as Clarke thought, disappear in the cervical and lumbar enlargements, 

 but that it is found throughout the whole length of the cord. While he admits that it 

 may disappear as a lateral horn in the cervical enlargement, he maintains that it is 

 continued upwards as the cells of the formatio reticularis. He is further in agreement 

 with Krause in thinking that the lateral horn of the dorsal region is not identical with 

 the lateral projection of the anterior cornua in the cervical and lumbar enlargements, and 

 that the cells of the intermedio-lateral tract are not mere transformations or modifica- 

 tions (Schwalbe, Erb, Obersteinkr, Quain) of the cells in the lateral part of the 

 anterior cornua, but are of altogether independent origin and nature. 



Sherrington {Journ. Physiol., 1892, p. 698), with reference to these conclusions 

 of Waldeyer's, says : " Waldeyer, in his description of the grouping of the cells in 

 the cord of the gorilla, says that the lateral horn cells are found throughout the cord in 

 all its segments, including those of the cervical and lumbar enlargements. He divides 

 the ganglion cells of the cord into as many as fourteen definite groups, attaching to each 

 a name, but treats the cells of the lateral reticular formation and those of the lateral 

 horn as one group (Mittelzellen). When he says that the cells of the lateral horn are 

 present in, for instance, the eighth and seventh cervical segments, his meaning is that there 

 are cells in the reticular formation at that level which he considers are cells of the 

 lateral horn, although that horn can no longer with certainty be recognised. But in 

 regions where the lateral horn exists there are cells in the lateral reticular formation as 

 well as in the lateral horn, and the assumption that the cells of the lateral reticular 

 formation, although somewhat similar to the cells of the lateral horn, are identical with 



