758 



VIII, p. 215 — 223) a few months before the appearance of Minot's 

 paper, had described the presence of efferent or motor fibers in the 

 dorsal roots of an embryo chick, confirming what had already been 

 stated by Cajal and Lenhossek ; so that on this basis there may be 

 recognised three real spinal nerve roots: dorsal, lateral and ventral, 

 the latter being fused with the dorsal. The extension of the cinerea 

 in some regions of the myel to form the so called lateral horn may 

 be correlated with the lateral root and tend to confirm the view of 

 its identity. 



This precocious division of the fibers in the ganglia of the 

 Desmognathus into three nerve trunks suggests quite naturally a 

 possible correlation with the presence of the three nerve roots. In 

 this animal the ventral root divides quite close to the myel and some 

 of the fibers bend quite abruptly to enter the dorsal and latero- 

 caudal nerve trunks. I am rather disinclined in this instance to 

 accept Schaffer's view that these connecting rami contain the motor 

 elements of the dorsal root and the sensory elements of the ventral 

 root; but believe that the fibers passing from the three nerve trunks 

 into the dorsal root are of an afferent or sensory character, while 

 those coming from the ventral root are efferent or motor in nature; 

 because it seems entirely unnecessary in the dorsal and lateral trunks, 

 where both kinds of fibers are represented as well as in the ventral, 

 to reverse their course and send some of the motor elements through 

 the dorsal root and some of the sensory through the ventral; or to 

 put it in another way, that the motor fibers from the dorsal root 

 and the sensory (?) from the ventral arrange themselves in the 

 ganglion in such a way that the nerves leaving the ganglion contain 

 motor or sensory fibers only, as the case may be. It is only just 

 to say that Schaffer's paper deals almost entirely with the ar- 

 rangement of the fibers in the myel itself and that the arrangement 

 in the ganglion is apparently an incidental observation, but his state- 

 ment, if carried to its logical conclusion, amounts to what has just 

 been said. 



A discussion of further histological details and the morpho- 

 logy of the brain of the Desmognathus is reserved for a later 

 publication. 



The Cornell University, Ithaca, N. Y., 

 May 19, 1894. 



