678 SE CRE TION 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 Luchsinger 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. Acad. d. sc, Paris, 1879, tome lxxxix. p. 11 ; 
Rev. interned, d. sc. biol., Paris, 1880, p. 115; and " Lecons sur les substances tox. et 
medic," tome i. pp. 148-149. 
2 Journ. de mM., 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 JVachr. v. d. k. Gesellsch. d. Wissensch. u. d. Georg.-Auy. Univ., Gbttingen, 1878, 
p. 102. 
8 Centralbl. f. d. med. Wissensch., Berlin, 1878, S. 721. 
