94 Journal of Comparative Neurology. 



published by Arnstein (36), on the nerve supply of the respira- 

 tory organs. Arnstein in this illustration, a portion of which 

 is reproduced in Fig. i, shows a sympathetic neuron, the cell 

 body and dendrites of which are situated in a small sympathetic 

 ganglion found in the posterior wall of the trachea, where 

 he was able to trace the neuraxis of said neuron into the mus- 

 cular tissue of the tracheal wall. Non-medulated nerve fibers 

 — the neuraxes of sympathetic neurons — can without difficulty 

 be stained in involuntary muscle tissue, but such fibers are usu- 

 ally woven into intricate plexuses, so that the tracing of a single 

 fiber with its branches, especially when of some length, be- 

 comes a matter of extreme difficulty. I have some few times 

 succeeded in doing this for neurons situated in Auerbach's 

 plexus. In fishes and reptilia the sympathetic cells of this 

 plexus are often quite isolated ; this is especially true of fishes, 

 where also the neuraxes are relatively short, so that in meth- 

 ylen-blue preparations the neuraxis could be traced from the 

 cell body to its ending in the involuntary muscle cells. The 

 neuraxes and dendrites of the neurons destined to innervate the 

 involuntary muscle are united into an intricate plexus, at the 

 nodes of which the cell bodies of the neurons are grouped into 

 small ganglia. From this plexus, smaller or larger bundles of 

 nerve fibers are given off, v/hich form a plexus around the fas- 

 ciculi of the muscle. This plexus is very well shown in the 

 bladder of the frog, where the fasciculi form an interlacing net- 

 work. From the plexus around the fasciculi, fibers or small 

 bundles of fibers are given off, which can often be traced for 

 longer or shorter distances between the muscle cells as they 

 course along in the intercellular cement, and where they run 

 parallel to the long axis of the muscle cells. 



The ultimate ending of these fibers in or on the muscle 

 cells has been a point much disputed ; two very distinct views be- 

 ing held until quite recently, Arnold (37), Frankenhauser (38), 

 Lustig (39) and Obregia (40) believing that the nerve fibers 

 terminate in the nuclei of the involuntary muscle cells, often 

 passing through the nucleus of one cell, again entering the inter- 

 muscular plexus, and entering another cell before terminating. 



