674 SECRETION AND ABSORPTION BY THE SKIN. 



commencing in the hind-limbs, slowing and final arrest of the heart, and 

 constriction of the pupil. Frogs, guinea-pigs, and small birds are killed by 

 injection of the alcoholic extract of the collection of glands forming the 

 so-called " parotids " of the toad. The poisonous substance is dialy sable, 

 and is probably an alkaloid. The blood of toads also contains small amounts 

 of this substance, and the serum of a toad will kill a frog if introduced into 

 the dorsal lymph sac. 



The slime of fish is secreted by goblet cells in the epidermis, but has been 

 little investigated from the chemical standpoint, on account of the great 

 difficulty in obtaining it in sufficient quantities, and free from foreign 

 substances. The slime of Myxine glutinosa is most easily obtained, and is 

 found to contain a mucin-like body, which, however, does not yield a 

 reducing sugar on boiling with dilute acicU 1 



The reaction of the skin of the eel and of Myxine is alkaline to litmus, 

 but curiously does not affect phenophthalein. A reducing sugar can be 

 obtained from the slime of the eel by boiling with dilute acid.' 2 According 

 to Alcock, 3 the slime of the Ammocwte larva yields a proteolytic ferment on 

 extraction. 



(5) Sebaceous secretions. Such secretions are formed by prolifera- 

 tion and subsequent degeneration of the cells lining the sebaceous 

 glands, in which karyokinetic figures are frequent. 4 



These glands are present over the whole surface of the body, with the 

 exception of the palms of the hands, soles of the feet, dorsal surface of the 

 third phalanges, and glans penis. 



Since it is impossible to collect sufficient quantities of the sebum of 

 man for analysis, w T e have to rest content with analyses of the contents 

 of sebaceous cysts, the vernix caseosa of the foetus, or the contents of 

 derinoid cysts of the ovary. 



Glycerin and cholesterin fats, fatty acids, albumin (casein ?), free 

 cholesterin and isocholesterin, with water and salts, are the main con- 

 stituents of sebum. 



The following table is taken from Hoppe-Seyler : 5 



1 Journ. Physiol., Cambridge and London, 1893, vol. xv. p. 488. 



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



3 Proc. Phil. Soc., Cambridge, 1891, vol. vii. pt. 5, p. 252. 

 4 Bizzozero and Vasale, Med. Ohir. Centralbl., Wien, 1884, S. 77 and 179. 

 5 "Physiol. Chem.," Berlin, 1881, Th. 4, S. 761. 



