680 SECRETION AND ABSORPTION B Y THE SKIN. 



secretion, when excitation of previously divided nerves is without effect, 

 pointing to stimulation of the gland protoplasm by the drug. 



According to Rossbach, 1 small doses act upon the nerve-endings, 

 while large doses also affect the gland protoplasm ; and some of the 

 experiments of Luchsinger, Marme, and Hogyes, in which pilocarpine 

 caused secretion, long after the time necessary for complete degeneration 

 of the nerves had elapsed, point to the same conclusion. 



There appears to be no central action by pilocarpine, for Eobillard, 2 

 after separating the foot of a cat from the body, with the exception of 

 the tibial nerve, obtained 110 secretion of sweat on injection of pilo- 

 carpine into the general circulation ; though the nerve was proved to 

 conduct, by a profuse sweat caused on asphyxiation. 



Muscarine 3 also acts as a peripheral excitant, but is less active than 

 pilocarpine. 



Atropine and duboisine are both antagonistic to pilocarpine and 

 muscarine. 



In the cat an injection into a vein of 3 mgrms. of atropine is sufficient 

 to make stimulation of the sciatic ineffective ; subsequent intravenous 

 injection of 10 mgrms. of pilocarpine will cause sweating, though the 

 nerve is still without action on excitation. In such a case the atropine 

 poisons the nerve-ending, but the gland protoplasm is still excitable and 

 responds to pilocarpine. According to Bossbach, 4 a dose of 20 to 30 

 mgrms. of atropine is needed, in the case of a cat, to paralyse the gland- 

 cells to such an extent that subsequent local application of pilocarpine 

 is without effect. All glandular apparatus appears to be far more 

 sensitive to atropine than to pilocarpine. 



The local paralysing effect of atropine was elegantly demonstrated 

 by Aubert. 5 If the palm or finger (carefully cleaned) is pressed on to 

 paper sensitised with silver nitrate, the spots of chloride formed at the 

 mouths of the sweat-ducts are quite visible. If the experiment is tried, 

 after a pad soaked in atropine solution has been tied over a limited 

 surface overnight, that surface is found to yield no spots, in contrast to 

 the surrounding field. 



Finally, the terminal sweat apparatus is very sensitive to change of 

 temperature. Luchsinger 6 has shown that not only cold but excessive 

 heating retards the action of the glands. Thus if, on a warm day, one 

 hand be held in water at 45 to 50 C. for ten minutes, while the other is 

 immersed in water at 15 to 30 C., and exercise is then taken, the hand 

 which was in water at the lower temperature commences to sweat at 

 once, the other not for some considerable time. In experimental work, 

 in which the excitation of nerves is undertaken and the outbreak of 

 sweat observed, the greatest caution is necessary to keep the tempera- 

 ture of the extremities constant, for with a cold foot a nerve root hold- 

 ing sweat-fibres in reality, may be wrongly considered to hold none, if 

 the terminal apparatus is depressed by cold. 



That the formation of sweat is a true act of secretion, and not 

 merely filtration, is shown by experiments already quoted, in which it is 

 noted that after stoppage of the circulation sweat is still secreted on 



1 Arch. f. d. ges. PhysioL, Bonn, 1880, Bd. xxi. S. 1. 2 Loc. cit. 



3 Triimpy and Luchsinger, Arch. f. d. ges. PhysioL, Bonn, 1878, Bd. xviii. S. 501 ; 

 Ott and Wood Field, Journ. PhysioL, Cambridge and London, 1878, vol. i. p. 193; 

 Hogyes, lac. cit. 



4 Loc. cit. 5 Lyon mid., 1874. 

 Arch.f. d. ges. PhysioL, Bonn, 1878, Bd. xviii. S. 478, 



