AFRANIO DO AMARAL 1067 



being the "fer-de-lance"; AgUstrodon Beauvois, which is the most widespread of all 

 the Crotalidae, for it occurs in the Palaearctic, Indian, Nearctic, and Neotropical 

 regions, being represented by the "copperhead" and the "cotton-mouth moccasin" 

 in the United States; Sistrurus Garman (main form — the "massasauga"), which is 

 peculiar to the eastern part of the Nearctic and to the extreme northern part of the 

 Neotropical region, and is probably in process of disappearance; Crotalus Linne, which 

 is common to both the Nearctic and the Neotropical regions, being represented by 

 only one species in the American tropics and by about a dozen or so in the United 

 States; and Lachesis Daudin, which, in my opinion, shows the highest degree of 

 differentiation among snakes and occurs in the Neotropical region, its only species, 

 the "bushmaster," L. mtita (L), being confined to Central and South America. 



POISON APPARATUS 



The venom apparatus consists of a gland, a duct, and one or more fangs located on each 

 side of the head. The venom is the secretion of the external supralabial gland of the ophid- 

 ians, which is found below and back of the orbit. It receives its blood supply from the "arteria 

 alveolaris inferior ramus glandulae maxillae superioris posterior" of Schlem and is innervated 

 by the "nervus labialis superior" which is one of the terminal branches of the trigeminal. 



Histologically, the gland is serous, although its secretion contains also a great deal of 

 mucus. This mucus is excreted both by cells found in the walls of the duct close to its ter- 

 mination, and by a great many alveoli which surround the duct. The size of the gland is 

 usually in proportion to the size of the snake. However, it is relatively larger in the so- 

 lenoglyphous type than in the proteroglyphous. Among the solenoglyphous, the Brazilian 

 "jararacussu," Bothrops jararacussu Lacerda, the Florida "diamond-back rattler," Crotalus 

 adamanteiis Beauvois, and the South American B. alternata Dum & Bibr., have the largest 

 glands, while the "bushmaster," Lachesis muta (L.), has the longest fangs. According to 

 Boulenger,' among the proteroglyphous, Doliophis bivirgata Boiehas the largest glands, which 

 "instead of being confined to the temporal region, extend along each side of the body for 

 about one-third of its length, gradually thickening and terminating in front of the heart 

 with club-shaped ends." Among solenoglyphous types the species of Causus show a similarly 

 aberrant glandular development. The longest fangs among proteroglyphous snakes are 

 found in Dendraspis antinorii Peters and other African species. 



The gland is surrounded by a fibrous capsule which represents a prolongation of the 

 zygomatic ligament and divides it into various segments or lobes receiving fibers from both 

 the anterior and the medium temporal muscles (S. Weir Mitchell). 



The duct of solenoglyphous snakes, emerging from the gland, tends upward, then for- 

 ward, and, finally, turning downward, opens abruptly through a small papilla on the anterior 

 wall of the mucous membrane which involves the base of the fangs. Sometimes the duct, at 

 its end, shows either a few muscular fibers which are connected with the internal pterygoid 

 muscle, as is the case with all the species of rattlesnakes (Crotalus), or a real smooth muscle, 

 as in the sea snakes (Disteiridae). These muscles, which serve as a sphincter to the duct, 

 also insure perfect connection between it and the base of the fang. 



VENOM INOCULATION (tHE ACT OF BITING) 



Fangs and jawbones are quite movable in the solenoglyphous and occasionally in some 

 aglyphou.s, viz., in the genus Ophis ( = Xenodon). Apparently, snakes have perfect control 



' Boulenger, G. A.: Cat. Sn., Brit. Miis., 3, 400. 1896. 



