VENOMS IN THE ANIMAL SEEIES 



291 



placed on the back of the fish. The wound is very painful, and is 

 accompanied by a series of alarming symptoms, which sometimes 

 terminate fatally : fishermen are consequently much afraid of it. 



There are a large number of species of this fish, peculiar to 

 different regions. Sijnanceia brachio (fig. 101), the largest specimens 

 of which attain the length of 45 cm., is the most common form in 

 the Tropical Pacific. 



4 A. .^- 



Fig. 101. — Synanceia brachio, var. verrucosa. (After Savtscbenko. 



The spiny rays of the dorsal fin of Synanceia are sharp-pointed, 

 stout in the middle, and provided on each side with a small canal 

 hollowed out in the thickness of the spine. Towards the middle of 

 the latter there is attached a little double sac, or kind of closed pouch, 

 which, on being compressed, allows the venom to escape in a thin 

 jet which flows into the grooves of the spine. The expulsion of the 

 venom is therefore not a voluntary act on the part of the fish ; in 

 order that it shall take place, pressure must be applied to the sacs in 

 which it is contained. 



This venom, when extracted from the glands, is limpid, bluish, 

 and slightly acid. When introduced into the tissues, it produces very 

 acute local pain, which extends throughout the affected limb. The 



