HuBER, Sympathetic Nervous System. 91 



touching on this point. After discussing the literature and re- 

 viewing his own work, he reaches the following conclusions : 



1. The neuraxes of sympathetic neurons become invested 

 in many cases with a thin medullary sheath, thus forming very 

 fine medullated fibers, which on account of their small size can 

 be differentiated from the smallest cerebro-spinal fibers. 



2. In some cases this thin sheath of myelin accompanies 

 the respective neuraxis to near its termination. Such fibers, 

 he states, are found in the ciliary branches of the ophthalmic 

 ganglion ; in the nerves innervating the muscles of the hair pa- 

 pilla; (cat) ; and many of the fibers of the sympathetic chain. 



3. In many of the sympathetic nerve fibers the medullary 

 sheath is sooner or later lost, the neuraxis continuing as a non- 

 medullated fiber; as for instance in the intestine, the liver, and 

 in some of the nerves going to the spleen. 



4. And finally the sympathetic system contains a large 

 number of fibers — neuraxes of sympathetic neurons — that are 

 non-medullated throughout their whole course. The great ma- 

 jority of the neuraxes of the neurons in the peripheral ganglia, 

 in the intestine, in glands and in the heart are fibers of this 

 nature. 



As regards .the structure of the neuraxes of sympathetic 

 neurons the following observations have been made — 



1. Dogiel (25) has shown that they consist of very fine 

 ultimate fibrillae, between which there is found a very small 

 amount of inter-fibrillar substance — the neuroplasma. 



2. Dogiel (25) further states that these neuraxes have as a 

 rule a very regular and smooth contour, and only now and then 

 small spindle-shaped enlargements, which resemble varicose 

 enlargements, are to be seen. My own observations would 

 lead me to modify this statement to this extent, — that only the 

 larger neuraxes of sympathetic neurons, such, I have reason to 

 believe, as are invested with a sheath of myelfn, show this 

 smooth contour ; while a great many of the neuraxes (such as re- 

 main non-medullated) show the typical varicose enlargements ; 

 it is true more often near their termination. The structure and 

 importance of such varicose enlargements is a point ooncerning 



