No. I.] SYMPATHETIC GANGLIA OF VERTEBRATES. 8 1 



It is probable, then, that in all vertebrates this statement 

 holds good : an impulse, leaving the cerebro-spinal system, and 

 having sympathetic effects, is transferred from a pre-ganglionic 

 fiber to one or several sympathetic cells which convey it along 

 their neuraxes to the periphery. 



The writer would here again offer the suggestion first made 

 in the lectures above referred to, that nicotin does not primarily 

 paralyze the sympathetic cells of the sympathetic ganglia, but 

 the pericellular plexuses, the endings of the pre-ganglionic fibers 

 in the sympathetic ganglia. This theory, for it is but a theory, 

 is based on the analogy which exists between the physiological 

 action of nicotin and certain other drugs, notably curare. The 

 latter drug, as is well known, paralyzes the motor endings in 

 striped muscle, and has an action very similar to nicotin on the 

 sympathetic ganglia ; on the other hand, nicotin paralyzes also 

 the motor endings in striated muscle, not quite so readily as 

 curare, but in a similar manner ; its action on the sympathetic 

 ganglia has already been explained. It would seem reasonable, 

 therefore, to suppose that, in both cases above alluded to, curare 

 and nicotin paralyze the ending of the cerebro-spinal fiber ; in 

 the one case, the motor ending in striped muscle ; in the other 

 case, the pericellular plexuses in the sympathetic ganglia.^ 



The question as to whether the neuraxes of sympathetic 

 cells may end in other sympathetic ganglia, and may in this 

 way influence other sympathetic cells, seems as yet open to 

 discussion. Kolliker and Langley are of the opinion that the 

 neuraxes of sympathetic neurons end always in the periphery, 

 in involuntary muscle, gland tissue, etc.; while Dogiel, with 

 whom my own observations on this point lead me to concur, 

 believes that the fine fibers, which end in, and help to form the 

 intercellular plexus of the sympathetic ganglia, are the neuraxes 

 of sympathetic neurons, more especially the myelinate ones. 

 They end, I believe, on the dendrites of the sympathetic neurons 

 of the ganglion. 



Histological Laboratory, University of Michigan, 

 July, 1897. 



1 In his later writings, Professor Langley gives this explanation of the action of 

 nicotin on the sympathetic ganglia. 



