Nr, 3 Zentralblatt für Physiologfie. I5I 



to »peak of them as forming one group. Since their terminations 

 broadly speaking are alongside those of the sympathetic the term 

 ,,para-sympathetic" is fairly descriptive of them. 



4. In the para-sympathetic system two divisions are closely 

 related phylogenetically. They have developed in connection with 

 the anterior and posterior involutions of the body wall which give 

 rise to the alimentary canal and respiratory tracts. These two then 

 can be put together to form the oro-anal system. The oral part arises 

 from the meduUa oblongata (bulbar autonomic), the anal part arises 

 from the sacral region of the spinal cord (sacral autonomic). 



5. The connections of the nerve cells of the plexuses of Auer- 

 bach and Meißner are unknown. A priori they might be expected 

 to belong to the oro-anal system, but there is no definite evidence 

 for this, and some against it. It is therefore better provisionally to 

 put them in a class by themselves as the enteric system. 



6. It will be Seen that the nomenclature is almost entirely 

 anatomical. On pharmacological grounds Heubner has recently 

 proposed to put the secretory sweat fibres into the class which I have 

 called para-sympathetic and to call the whole ,,concensuel". If thic 

 is done, is should be clearly understood that the term consensual 

 has no anatomical justification. The pharmacological difficulty 

 seems to me to depend upon the hypothesis that adrenalin, atropine, 

 Pilocarpine, and other such drugs with specific effects, act upon 

 nerve endings. On this hypothesis, adrenalin should cause a secretion 

 of sweat and Pilocarpine should not do so. Since adrenalin does not 

 cause a secretion, and Pilocarpine does, there is obviously something 

 wrong with the hypothesis. If however, as I have argued, these drugs 

 have no special action on nerve endings, but act direct on the tissue, 

 these difficulties disappear, though it is true other problems arise. 

 The reaction of tissues to specific poisons is I consider related to 

 their phylogenetic history. The tissues innervated by the para- 

 sympathetic System, as has been pointed out by the Vienna School, 

 react in general to the same specific poisons. This, I take it, is because 

 they have developed at approximately the same time and in appro- 

 ximately the same chemical conditions. The tissues innervated by 

 the sympathetic react in general to other specific poisons because 

 they have developed at a different time and in other chemical con- 

 ditions ; one of these conditions is the simultaneous formation of 

 adrenalin. The nerve supplying a tissue increases its chemical changes 

 and so affords greater opportunities of chemical Variation, but the 

 chemical Variation does not I think depend upon the kind of nerve 

 with which it is connected, and probably any nerve causing equal 

 chemical change would have the same effect. On this theory we should 

 expect that there would be differences in the pharmacological beha- 

 viour of tissues innervated by the same system of nerves, and the 

 action of specific poisons becomes more explicable. Thus the muscies 

 of the hairs and the sweat glands are of different phylogenetic data 

 from most at any rate of the other tissues innervated by sympathetic 

 nerves. Their chemical liistory is different; this is especially the case 



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