NICOTINE. 515 



I have tried both methods 1 in observations on the effects of 

 pilocarpine and atropine upon the submaxillary gland of the cat and 

 dog. The latter method is much simpler, and seems to me better. An 

 experiment, briefly stated, is as follows. A paralysing dose of atropine 

 is injected into a body vein. A cannula filled with a 2 to 4 per cent, 

 solution of pilocarpine nitrate is tied into Wharton's duct, and 01 to 0*25 

 per cent, of the solution driven into the gland. This causes a secretion 

 of saliva and great increase of blood flow, lasting several minutes, but 

 steadily lessening in rate. During the flow of saliva the chorda 

 tympani becomes again irritable, and may remain so for a short time 

 after pilocarpine has ceased to produce a secretion. As the pilocarpine 

 is carried out of the gland by the secretion, by the blood, and by the 

 lymph, the atropine continually flowing to the gland in the blood again 

 acquires the upper hand, and the nerve-endings become again paralysed. 

 With renewed injection of pilocarpine there is renewed transient secre- 

 tion and renewed transient irritability of the chorda tympani. And 

 the paralysis and recovery may be repeated many times in an hour. 

 It is, however, to be noticed, that if more than the minimal dose of 

 atropine be given, more than one injection of pilocarpine may be required. 



Although pilocarpine can instantaneously restore some degree of activity to 

 the chorda tympani which has been paralysed by atropine, yet the activity is 

 always considerably less than normal. 



In the cat, when the cervical sympathetic has been paralysed by atropine, 

 its activity can be restored by injecting pilocarpine into the duct, although 

 pilocarpine does not stimulate the secretory nerve endings of the sympathetic. 



Nicotine. Nicotine causes a brief flow of saliva, followed by a 

 temporary paralysis of the cranial and sympathetic fibres 2 up to their 

 connections with the peripheral ganglia. 3 We have already described the 

 main features of this paralysis in connection with the chorda tympani, 

 and in connection with the sympathetic (p. 480). In all the mammals 

 which have been experimented on, small doses of nicotine readily pro- 

 duce excitatory effects, but the amount required to paralyse the secretory 

 and vasomotor preganglionic fibres varies widely in different cases. 

 Moreover, the minimal amount required to produce paralysis is not 

 precisely the same for fibres of different origin, or for fibres of similar 

 origin but different function. In the rabbit and cat the differences are 

 not great, the amount required varying from about 5 to about 10 mgrms. 

 In these animals about 10 mgrms. of nicotine injected into the blood 

 will cause a paralysis of preganglionic fibres lasting about fifteen 

 minutes. In the dog, 30 to 40 mgrms. have a similar effect on the chorda 

 tympani, in so far that, usually, stimulation of the chorda for about twenty 

 seconds causes no secretion ; but in some cases, at any rate, and even 

 after larger doses, more protracted stimulation of the chorda induces 

 gradually an active and protracted secretion, 4 continuing for some time 

 after the cessation of the stimulus. And very large doses may be 

 given to a dog without paralysing completely the cervical sympathetic. 



1 Journ. Anat. and PhysioL, London, 1876, vol. xi. p. 173 ; Journ. PhysioL, Cam- 

 bridge and London, 1878, vol. i. p. 339 ; 1880, vol. iii. p. 2. For method of injecting into 

 the gland arteries, cf. Heidenhain, op. cit., 1874. 



" Heidenhain, Arch. f. d. ges. PhysioL, Bonn, 1872, Bd. v. S. 316. 



3 Langley and Dickinson, Proc. Roy. Soc. London, 1889, vol. xvi. p. 423 ; Langley, 

 Journ. PfiysioL, Cambridge and London, 1890, vol. xi. p. 123. 



4 Repeated doses have a tendency to cause in the dog a continuous secretion. 



