ELECTRO-MOTIVE PHENOMENA IN SKIN GLANDS. 681 



excitation of nerves ; and further, by the fact that by means of atropine 

 the secretion of sweat can be stopped in spite of the continued circula- 

 tion of the blood. 



It is probably right to conclude that the blood supply is a necessary 

 adjuvant to the prolonged activity of the gland-cells, but not the stimu- 

 lant to their action, though, according to Levy, 1 secretion is provoked 

 upon reinstallation of the circulation, in a limb with cut sciatic, which 

 has been long kept anaemic. This effect may possibly be due to the 

 mechanical stimulation of the glands by the pulse. 



Levy Dorn 2 placed the hind-limb of a cat in a receptacle within 

 which the air pressure could be raised, and found that the secretion 

 could overcome a pressure in excess of that in the large arteries. 



Nothing is definitely known as to the existence or not of any 

 action of the nervous system upon the sebaceous glands. 



According to Arloing, 3 section of the cervical sympathetic in 

 donkeys causes exudation of sebum from the sebaceous glands of the 

 skin of the ear, reaching its maximum fifteen hours after section, and 

 lasting for sixty-four hours. Stimulation of the peripheral end of the 

 nerve also causes secretion from these glands. 



The glands of the skin of the frog undergo periodic contraction and expan- 

 sion by means of their muscular sheaths, 4 and have been carefully studied by 

 Engelmann, 5 Strieker and Spina, 6 and Drasch, 7 in the web and membrana 

 nictitans. The spontaneous movements in the case of the -web glands are 

 stopped temporarily by section of the sciatic, or seventh, eighth, and ninth 

 anterior spinal roots. Excitation of the sciatic or reflex stimulation of the skin 

 leads to contraction of the glands, as also does direct excitation by vapours of 

 chloroform or ether, or by carbonic acid gas. During contraction of the whole 

 gland, by its muscular sheath, the lining gland-cells swell, and, according to 

 Drasch, in the case of the membrana nictitans, the fifth cranial nerve, on ex- 

 citation, causes contraction of the sheath only, while excitation of the sympa- 

 thetic causes swelling of the cells. Pilocarpine causes increased secretion by 

 these glands. Strieker and Spina advanced a theory of secretion based upon 

 observations of these glands, maintaining that, in the act of swelling, fluid is 

 sucked in by the cells from the surrounding lymph spaces, and on contraction 

 forced out into the lumen ; the theory obviously involves the assumption of some 

 valvular structure in the protoplasm, of which we know nothing, and furthermore 

 has been disposed of by Drasch, who has found that the glands of the mem- 

 brana nictitans may secrete freely in stages of immobility of the lining cells. 



In the case of fish in the eel it has been shown that the secretion of the 

 goblet cells of the epidermis and of the club cells (when present) is under the 

 influence of the nervous system, but the nerve paths have not been worked out. 8 



ELECTRO-MOTIVE PHENOMENA IN SKIN GLANDS. 



In attempting to demonstrate the existence of currents in the 

 uninjured muscles of the frog, du Bois Eeymond 9 discovered that the 



1 Loc. cit. . 



2 " Verhandl. d. Berl. physiol. Gesellsch.," Arch. f. PhysioL, Leipzig, 1893, S. 383. 



3 Arch, de physiol. norm, etpath., Paris, 1891, Se"r. 5, tome iii. p. 241. 



4 Ascherson, Arch. f. Anat. u. PhysioL, Leipzig, 1840, S. 15. 



5 Arch.f. d. ges. PhysioL, Bonn, 1872, Bd. v. S. 498. 



6 Sitzungsb. d. k. Akad. d. Wissensch., Wien, 1880, Bd. Ixxx. Abth. 3, S. 95. 



7 Arch.f. PhysioL, Leipzig, 1889, S. 96. 



8 Reid, Phil. Trans., London, 1894, vol. clxxxv. p. 319. 



9 " Uiitersuch. ueber thierische Elektricitlit," Bd. ii. Abth. 2, S. 9-20. 



