TUBERCULIN AND MALLEIN 179 



poison which stands boiling. This poison, in nature, is 

 dangerous to crabs and fishes ; in the laboratory it is found 

 to kill the rabbit. 



Among the Arthropoda, the Spiders and Scorpions (Arach- 

 nidse) secrete active poisons. The excretory tubes of the 

 poison glands of venomous spiders open at the point of the 

 two appendices which are furnished with claws at the end and 

 situated on each side of the mouth. The poison kills the 

 small animals on which the spiders feed, and causes in man 

 pain and contracture at the bitten point — a sort of miniature 

 tetanus. The poison of certain spiders contains a haemolysin, 

 i.e., it lakes blood, rtiaking the hsemoglobin of the corpuscles 

 diffuse into the surrounding liquid (arachnolysin). The bite 

 of the Tarantula {Lycosa tarentuld) is only dangerous for the 

 small animals on which they feed, and is quite harmless to 

 man. According to Brehm, all the stories of the effects on 

 man of the Tarantula bite are nothing but fables and 

 fantasies. 



The venom of the Scorpion {Scorpio occitanus) of the South 

 of France can kill a guinea-pig in a dose of half a milligram of 

 dry extract ; for a rabbit one milligram. The scorpion is the 

 subject of a legend which says that when it is enclosed by a 

 circle of fire it commits suicide with its own poison. Now 

 the scorpion is in reality immune to scorpion venom, towards 

 which its serum acts like an antitoxin (Metchnikoff). 



Among the Myriapoda the Centipedes, and among insects the 

 Hymenoptera, secrete venoms. The poison extracted from two 

 bees (by grinding up the terminal part of their bodies in i c.c. 

 of water) is sufficient to kill by asphyxia a mouse or a 

 sparrow. It also is a hsemolytic poison. 



There are many poisonous fishes. As a rule their poison 

 glands are found at the base of the dorsal or caudal fins, or 

 under the spine of the gill-flap. These venoms all resemble 

 more or less that of the weever-fish, which has been most 

 studied. Locally it causes pain and swelling, with fever and 

 vomiting. At the time of spawning the poison is more 

 abundant and more active. The tropical tetrodons are most 



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