THE SECRETION OF SWEAT. 679 
result in a few cases with divided cord. Obviously a positive case in 
such an experiment is worth many negative, since the excitability of 
tin' cord below the Bection may possibly 1m- depressed at the time of 
making the test. It is generally accepted that spinal u sweat-centres" 
exist. 
On the other haml. no cerebral centres for sweating have yet been 
experimentally demonstrated. 1 
According to Levy Dorn, 2 the spinal "sweat-centres" are very re- 
sistant to the action of cold. In eats cooled till the rectal temperature 
was 22° to 28° C, sweating was still obtained by reflex excitation or 
dyspnoea, but heating (70 < '. ) caused little sweating, the cooled cal 
being as it were " protected," in that the heat which is to restore it, 
does not, when applied, immediately call forth a reflex outpouring of 
sweat, by the subsequent evaporation of which, heat would be abstracted 
from the body. 
The nervous mechanism of sweat secretion may be called into action 
by central stimuli, by reflex action, or by peripheral stimuli. A venous 
condition of the blood is one of the most active stimuli to the central 
mechanism, and one frequently employed in experimental work. If an 
animal be partially asphyxiated, after section of the spinal cord in the 
mid-dorsal region, sweat breaks out on the pads of the hind-feet, even 
after division of all the posterior roots behind the section. 3 
Eaising the temperature of the blood produces a similar effect, and 
the result is also obtained with divided posterior roots, and hence is not 
reflex ; moreover, the effect is stopped by section of the sciatic, and hence 
is not of peripheral origin as a result of heating of the terminal apparatus. 
Certain drugs, especially picrotoxin and strychnia, appear to cause 
sweating exclusively by their action on the spinal cord. Nicotine and 
eserine cause slight sweating after section of the limb nerves, and are 
therefore not exclusively, though mainly, central stimulants. 4 
Eeflexly, it may be broadly stated that stimulation of almost any 
afferent channel will cause sweating. A cat will sweat on the pads of 
its feet at the sight of a dog, mustard in the mouth causes sweat on the 
foreheads of many persons, and the application of heat to the skin is a 
familiar cause of increased action of the glands. According to Greiden- 
berg, 5 in a patient with sweating legs, slight skin stimuli diminished the 
secretion, while strong stimuli caused an increase. 
Directly from the periphery, the sweat-glands may be excited by 
certain drugs or by raising their temperature. 
Pilocarpine excites secretion of sweat after complete division of the 
nerves, and localised secretion may lie produced by introducing it 
beneath the skin. Its action is probably in the main upon the termina- 
tions of the nerves in the glands, since it is, as a rule, non-effective, when 
sufficient time has been allowed to elapjse after section of the nerves to 
ensure complete degeneration (Luchsinger, Xawroeki, and Yulpian). On 
the other hand, Max Levy 6 states that pilocarpine may still give good 
1 Bloch, "These de Paris," 1S80. 
- "Yerhandl. d. Bed. physiol. Gesellsch.," hi Arch. f. Physiol., Leipzig, 1895, S. 198. 
3 Luchsinger, Arch. f. d. yes. Physiol., Bonn, 1877, Bd. xiv. S. 369. ; Robillard, 
"These de Doct./' Lille, 1880. 
4 Luchsinger, Arch. f. d. yes. Physiol., Bonn, 1877, Bd. xv. S. 482; Hogyes, ref. in 
Jahresb. ii. d. Fortschr. d. A not. n. Physiol., Leipzig, 1881, Bd. ix. S. I'l. 
5 Jahresb. ii. '/. Fortschr. d. Anat. u. Physiol., Leipzig. 1882, Bd. x. S. 81. 
6 Centralbl.f. Physiol., Leipzig u. AVien, 1892, Bd. v. S. 68. 
