634 'Journal of Comparative Neurology and Psychology. 



If we examine Corning's figures, one of which is reproduced 

 in fig. 8, we can see that the bud which is to form the limb muscles 

 grows distinctly from the lateral part of the myotome, quite 

 separate from the ventral tip from which the body muscles are to 

 arise, so that van Bisselick's three portions are indicated. The 

 cells which are to form the dorsal muscles are also laterally situated, 

 and it seems to me that there is at least as much reason to group 

 the two lateral portions of the myotome, the dorso-lateral and the 

 ventro-lateral cells, and to consider that they give rise to similar 

 muscles, as to group the ventral and the ventro-lateral portions. 

 In other words, I consider the muscles of the limbs as homologous 

 with the muscles of the back and therefore to be supplied by the 

 same nerve components. 



Johnston is satisfied to speak of his somatic and visceral motor 

 components as arising from cells in the anterior and lateral horns 

 of the cord, respectively; but the researches, anatomical and 

 physiological, of many workers tend to show that in these broad 

 areas there are several more or less clearly defined groups of cells 

 which have received names, as the ventro-mesial group, the ventro- 

 lateral group, the dorso-mesial group, etc. Experiments have 

 been made to prove that these different groups are the nuclei of 

 origin of certain anatomical nerves, but Lapinsky (1904. i), in 

 a very elaborate set of tables, shows that this idea has been 

 carried too far; that the fibers to one muscle may arise in several 

 of these cell groups in several segments of the cord, and that these 

 minor groupings are unimportant. A few facts stand out clearly 

 however: there is ( i ) a median group or groups of cells, extending 

 as a column throughout the cord from the sacral region, and of 

 practically uniform size except for an enlargement at the lower 

 cervical segments; (2) a lateral, or ventro-lateral group also 

 extending throughout the cord, but showing a large mcrease in 

 size at the lumbar and cervical enlargements; and (3) a more pos- 

 terior group, described by Johnston as lying between the ventral 

 and dorsal horns, forming the lateral horn; by Santee (1907) as 

 "center of the crescent cells," which is not continuous, but present 

 (in the cord) only in the regions of the white rami communicantes 

 of the sympathetic system, and in the region of the roots of the 

 accessory nerve. Both these authors agree that this last group 

 (3) is made of the nerve cells whose axons run to the sympathetic 

 ganglia, and form Johnston's visceral efferent component; with 

 this I agree. 



