CHAPTER V. 



POISON APPARATUS OF VENOMOUS SNAKES. 



Venomous snakes in the act of biting inject a poisonous fluid into the 

 object bitten. This fluid is generally known as "venom" and is the product 

 of highly specialized, well-developed glands which show certain phylogenetic 

 relations to supralabial glands and correspond with the mouth-angle glands 

 of birds and the parotid glands of mammals. The fluid is injected into the 

 victim by means of a series of specialized teeth of the maxilla, which differ 

 from ordinary teeth by the presence of a groove throughout the entire front 

 surface of the teeth or of a complete canal from the base to the apex. These 

 speciahzed teeth, called "venom fangs," are larger than the rest, and are in 

 communication with the venom glands by means of the common ducts of 

 the latter. The end of the excretory ducts does not enter the basal opening 

 of the groove or canal of the poison fang, but opens quite close to the latter. 

 The flowing out of the venom is, however, well prevented by a sheath, which 

 is merely a prolongation or fold of the mucous membrane. Naturally the 

 inoculation itself is accomplished by the complicated motion of numerous 

 muscles, which open the mouth, erect the fangs, and close the mouth. Simul- 

 taneous compression of the venom glands by a certain muscular envelopment 

 forces out the glandular secretion through the common duct into the venom- 

 conducting fangs, which are in the meantime inserted into the victim. 



POISON FANGS. 



The specialized teeth adapted to conduct the secretion of the venom glands 

 into the interior of the tissue of the victim have certain general features com- 

 mon to widely distant families of venomous serpents. They are provided 

 with either a groove or a canal, and are larger in dimension than the rest of 

 the maxillary, palatine, and mandibular teeth. They are situated on the max- 

 illary bones, to which they are firmly ankylosed. The poison fangs are cres- 

 cent-shaped, with one square, wide end on the base. When in connection with 

 the maxillary bone and ectopterygoid bone (transversum) they resemble a 

 sickle. The base of the fang is, comparatively, very broad and the apex is 

 extremely sharp. In all proteroglyphous snakes the number of active fangs 

 is usually two, arranged side by side. Behind the inner fang are several 

 reserve fangs in developing order, which take the place of the active fang 

 when it is damaged or shed. In one set of proteroglypha the fangs are front- 

 ally grooved longitudinally, while in the other set the groove is completely 

 closed into a hollow tube which again opens as a slit near the frontal side of 

 the apex. This latter set is often designated solenoglypha or tubular-fanged. 

 The furrow of the groove is of varying depth, according to the species of the 

 snake. 



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