678 SECRETION AND ABSORPTION B Y THE SKIN. 



poraneous excitation of cut sciatic and abdominal sympathetic causes less sweat 

 on the pads of a cat's feet than excitation of sciatic alone, and the sweat- 

 stimulating drug pilocarpine causes more sweating when sciatic or sympathetic 

 are cut than intact. 



Later, Vulpian 1 abandoned this theory. He was led to the idea of the 

 existence of inhibitory fibres in the cervical sympathetic by consideration of 

 the old experiment of Dupuy, 2 in which section of the cervical sympathetic 

 in the horse leads to sweating on the face on the side of section. Mere excess 

 of blood supply to sweat-glands, from the vaso-dilation which occurs simul- 

 taneously, is probably per se no stimulus to the action, 3 but there is no doubt 

 that the excitability of the glands is thereby raised, and if, with Luchsinger, 4 

 it is admitted that a few sweat-fibres originate with the fifth cranial nerve, the 

 result is simply due to painful reflex, for J.uchsinger got no sweating on section 

 of the sympathetic in the neck of a chloralised horse, though stimulation of 

 the peripheral end gave abundance. 



The evidence adduced by Ott is the immediate cessation of a secretion pre- 

 viously evoked by pilocarpine, on excitation of the peripheral end of the 

 divided sciatic. Even if it were admissible that the accompanying vasomotor 

 constriction could cause the effect (which it is not, seeing that in the ampu- 

 tated foot sweat can still be called forth), the result, he maintains, is obtained 

 too suddenly to be accounted for in this manner. 



Again, he states that irritation of the abdominal sympathetic causes a 

 dryness of the pads of the foot on the side of irritation, and that pilocarpine 

 accentuates the difference in condition between the foot on the side of irrita- 

 tion and the normal foot on the opposite side. 



Finally, division of the abdominal sympathetic produces moist pads on the 

 side of section, and injection of pilocarpine makes these pads sweat before the 

 others. 



In Arloing's experiments on oxen and donkeys, the cervical sympathetic is 

 divided, and time is allowed to elapse until the vaso-dilation has passed off. 

 Pilocarpine now produces more marked secretion on the side of section, which 

 is interpreted as meaning that inhibitory impulses, restraining the action of the 

 glands on the sound side, have been removed on the side of section. 



It has always been a matter of difficulty to differentiate the action of two 

 oppositely acting sets of fibres running in the same nerve-trunk, and it must 

 be admitted that the evidence so far for the existence of inhibitory fibres for 

 sweat secretion is not strong. 



Excitation by appropriate stimuli of the regions of the spinal cord 

 from which the sweat-fibres emerge leads to an outpouring of sweat on 

 the parts of the skin supplied by these fibres. Thus, if the spinal cord 

 is divided above the exit of the twelfth thoracic nerve in the cat, and 

 the animal exposed to heat (60 to 70 C. for five to ten minutes), sweating 

 still occurs on the hind-limbs. 5 



Nawrocki 6 and Marine' 7 denied this effect, and maintained that it 

 is only when there is continuity of the cord with the bulb that such 

 stimulation causes sweating. Later, however, Nawrocki 8 obtained the 



1 Vulpian et Raymond, Compt. rend. Aead. d. sc., Paris, 1879, tome Ixxxix. p. 11 ; 

 Rev. internal, d. sc. UoL, Paris, 1880, p. 115; and " Lecons sur les substances tox. et 

 me"dic.," tome i. pp. 148-149. 



2 Journ. de me'd., chir., pharm., etc., Paris, 1816, tome xxxvii. 



3 But see Levy, " Verhandl. d. Berl. physiol. Gesellsch.," in Arch.f. Physiol., Leipzig, 

 1892, S. 155. 



4 Tagebl. d. Versamml. deutsch. Naturf. in Baden-Baden, 1879. 



5 Luchsinger, loc. cit. 6 Centralbl. f. d. med. Wissensch., Wien, 1878, S. 17. 



7 Nadir, v. d. k. Gesellsch. d. Wissensch. u. d. Georg.-Aug. Univ., Gb'ttingen, 1878, 

 p. 102. 



8 Centralbl. f. d. med. Wissensch., Berlin, 1878, S. 721. 



