THE SUPRARENAL SYSTEM 195 



It is evident from this that the effects of nicotine are confined 

 to the vegetative nervous system, for the efferent fibres of the 

 cerebro-spinal system are nowhere interrupted by ganglia. Such 

 being the case, nicotine may be used to determine whether certain 

 results are due to stimulation of the vegetative or of the animal 

 system ; moreover, it will decide the question as to whether or not 

 certain ganglia act as physiological commutators to certain nerve 

 fibres. Anatomical investigation shows that each vegetative nerve 

 contains several ganglia, but it is evident from the effects produced 

 by nicotine that an actual interruption in transmission occurs at 

 one point only in its course. 



The elective action of other toxic substances upon the vegeta- 

 tive nervous system serves to differentiate between the activity of 

 the sympathetic and the autonomous nerves. The elective, and at 

 the same time antagonistic, effects produced upon certain organs 

 and organic functions, by atropine on the one hand and by the 

 so-called muscarine group of substances (muscarine, pilocarpine, 

 physostigmine) on the other, have long been recognized and have, 

 in a certain measure, been turned to account for therapeutic pur- 

 poses. The substances of the muscarine group exercise a stimu- 

 latory effect upon those functions which are inhibited by atropine. 

 Closer investigation shows that the organs influenced by these 

 substances are exclusively those which possess an autonomous 

 innervation, such as the eye, the salivary glands, and the organs 

 supplied by the vagus nerve, namely, the heart, the bronchial mus- 

 culature, and gastro-intestinal canal. The sweat-glands form a 

 remarkable exception, for, although they are equally affected by 

 the action of these toxins, their innervation, as far as we know at 

 present, is entirely sympathetic. Moreover, as will readily be 

 seen by referring to the table on pp. 192 and 193, 

 the stimulatory action of pilocarpine, as representative of 

 the muscarine group, and the inhibitory action of atropine, 

 do not extend to all the nervous effects produced by 

 the autonomous system, but are confined to those whose 

 influence consists in the promotion of function. Pilocar- 

 pine is, then, a toxin which promotes autonomous activity; 

 atropine is a toxin which inhibits autonomous activity. In the 

 case of the heart muscle, on the contrary, the action of pilocarpine 

 is inhibitory, while that of atropine is stimulating. Frohlich and 

 Lowi were able to prove that the nitrites are also inhibitory toxins 

 whose action is confined to the autonomous nerve endings, but 

 that their influence is extended solely to those whose function is 

 inhibition. 



Adrenalin is a substance possessing an elective affinity for 

 the sympathetic system. The foundation for this theory will be 

 fully discussed in the following chapter. It will be seen from 

 the table given above (pp. 192 and 193) that adrenalin affects those 

 tissues only which have a sympathetic innervation ; and that its 

 effects are identical with those which may be obtained by stimu- 



