PILOCARPINE AND MUSCARINE. 513 



comparatively large close of atropine. 1 In the dog more than 100 

 mgrms. may be injected into a vein, and still secretion will be obtained 

 from the submaxillary gland by stimulating the cervical sympathetic. 

 In the cat this nerve ceases to cause a secretion after about 30 mgrms. 

 of atropine have been given. 2 



The point of action of atropine is the termination of the nerve-fibres 

 around the gland-cells. There are several facts which show this. We 

 may mention the following : In the case of the submaxillary gland, 

 when a dose of atropine has been given just sufficient to paralyse the 

 chorda tympani, 110 secretion is obtained by stimulating peripherally of 

 the (true) submaxillary ganglion; i.e., the postganglionic nerve-fibres 

 cause no secretion. Atropine applied directly to nerve-fibres whether 

 preganglionic or postganglionic in their course towards a tissue, does 

 not paralyse them. The paralysis produced by it must then be either 

 one of nerve-endings or of gland-cells. But in the case we are consider- 

 ing the gland-cells are not paralysed, since they are at once set secreting 

 by stimulating the cervical sympathetic. Hence we conclude that 

 atropine acts upon and paralyses the nerve-endings of the postganglionic 

 secretory fibres of the chorda tympani. And we may conclude, further, 

 that in other cases in which atropine paralyses secretory nerves, it has 

 this effect in consequence of an action upon the nerve-endings in the 

 gland. 



The exact method of action of atropine we can only guess at ; we might 

 suppose, either that it annuls the conductivity of the nerve-endings, or that 

 it causes a retraction of the terminal filaments, in the manner suggested by 

 Duval and others for the processes of nerve-cells in general, so that nervous 

 impulses can no longer pass from the nerve-endings to the gland-cells. 



Atropine does not paralyse the vaso-dilator fibres which accompany 

 the cranial secretory nerves. This was first shown by Heidenhain 3 in 

 the case of the chorda tympani of the dog. It is true that, when large 

 doses of atropine are given, both vaso-dilator and vaso-constrictor glandular 

 nerves produce less effect than normal, but there is nothing to show that 

 this action is in any way specific. 



Pilocarpine and muscarine. Both pilocarpine and muscarine pro- 

 duce copious and prolonged secretion, when given in very small quantity ; 

 for example, when 1 or 2 mgrms. are injected into the blood. 4 The 

 secretion when it slackens is increased by a further dose of the alkaloid, 

 so that the flow of saliva can be kept up for a very long time, apparently 

 indefinitely. A large dose is not required in order to produce the 

 maximum rate of flow, its effect is rather to increase the duration of the 

 flow. The saliva obtained is like that produced by stimulating the 

 cerebral nerve, and the secretion is accompanied by a great dilation of 

 the vessels of the gland. 



The secretion to which these alkaloids give rise from the submaxillary 

 gland is unaffected by section of the chorda tympani, or by extirpation 

 of the superior cervical ganglion ; it occurs after the connections of the 

 chorda tympani with the local nerve-cells have been paralysed by 



1 Heidenhain, op. cit. 



2 Langley, Journ. Physiol., Cambridge, 1878, vol. i. p. 98. 



3 Op. cit., supra. 



4 The chief features of the action of muscarine were described, "Das Muscarin," Leipzig, 

 by Schmiedeberg u. Koppe in 1869. 



VOL. i. 33 



