VENOM 235 



In the maxilla the only teeth are the poison-fangs 

 one or two large tubular fangs ankylosed to the bone and 

 a bunch of unattached "reserve" fangs behind. 



Viperidce are not found in the Australian region or in 

 Madagascar, but occur in Europe, Asia, Africa, and 

 America. They are divided into two subfamilies, 

 Viperince and Crotalince. 



(i) Viperince. Ordinary vipers without a loreal pit. 

 About forty-five species, of which more than half are 

 African, and the others are found in Asia and Europe : 

 some of the species have a wide range, and are common 

 to Europe and Asia, or to Asia and Africaner even, rarely, 

 to all three continents. None in America. 



(ii) Crotalince. Vipers with a large sensory pit the 

 loreal pit between the eye and the nostril. About sixty- 

 five species, of which nearly two-thirds are American 

 and the remainder Asiatic. Among the American species 

 the rattlesnakes are included. 



2. THE VENOM-APPARATUS AND VENOM OF 

 THANATOPHIUIA. 



The Venom Apparatus. The venom is secreted by a 

 pair of glands which are commonly regarded as homo- 

 logous with the parotids of mammals : it is injected by 

 special fangs situated in the front of the maxillae, and is 

 conveyed from the gland by a short duct, the end of 

 which is merely applied, not attached, to the base of 

 the fang. 



The gland is a racemose or tubulo-racemose gland, 

 enclosed in a tough fibrous capsule (fig. 101). As a rule 

 it is about the size and shape of a shelled almond, and 

 lies, on either side, in the temporal region immediately 

 behind the eye (fig, 101, gl.) ; but it occasionally has the 

 form of a long cord or ribbon extending far back in the 

 anterior third of the body. It is for the most part sub- 

 cutaneous, but in glands of the usual form its posterior 

 portion is covered by the fascia and some fibres of the 



