3g8 SCIENCE PROGRESS. 



termed the parotid gland. These are the " venom glands " 

 and their secretion, the "venom," is a white milky fluid, 

 intensely bitter and somewhat acrid to the taste, which 

 exudes on pressure, on electrical stimulation, or after death 

 by chloroform narcosis ; in the latter case every gland will 

 be found to be tipped by a white milky bead of the secre- 

 tion. 



Several observers (i) have studied the histological 

 characters of these glands, which, as they have essentially 

 the same structure in each animal, may be described 

 together. The gland follicles are more or less globular 

 and communicate with the surface by a short duct. The 

 lininof membrane of the larger follicles is throwii into folds 

 forming- imperfect septa which project into its cavity and 

 are covered with a flattened epithelium. In the smaller 

 follicles these septa are wanting, and the lining epithelium 

 is more or less cubical. The walls of the follicles are 

 plentifully supplied with nerves and blood-vessels. 



That these cutaneous glands in both the toad and 

 salamander really do secrete a venom which is extremely 

 toxic when introduced into the circulation is acknowledged 

 by, and is moreover conclusively proved by the experiments 

 of, all investigators with the exception of Davy (2 and 3) 

 and Rainey (1) who failed to observe any ill effect from the 

 secretion of the toad, their failure being due perhaps either 

 to the administration of too small a quantity of the venom, 

 or because of its non-absorption into the circulation, probably 

 the latter. The production of venom is by no means con- 

 fined to the common toad and land salamander, but is met 

 with in allied species, — the natterjack and tropical toads, 

 the tritons, and to a small extent the frogs. The creatures 

 are unable voluntarily to eject the venom, which is secreted 

 only in response to some reflex irritation and has a purely 

 defensive function. 



Pelletier {4) in 181 7 appears to have been the first to 

 investigate chemically the venom of the toad. He found 

 that it was acid in reaction and partially soluble in alcohol. 

 A fuller examination was made by Davy (2) in 1826 who 

 describes it as a yellowish thick fluid the greater part of 



