KEPTILIA. 259 



of Benclroaspis {Hamadryas) and of some other ludian snakes red- 

 dens litmus paper slightly'. The same feet is noticed by Harlan 

 with regard to Crotalus^. In common with other animal poisons 

 and contagious matters a very small quantity is sufficient to produce 

 the eflect. The poison of serpents is innocuous, if introduced into 

 the digestive passages by swallowing, but shews its natural action 

 when, by a wound or by being introduced into a vein, it enters the 

 current of the blood. The bite of all venomous serpents is not 

 equally dangerous to man; of some the effect is extraordinarily 

 rapid ; death mostly occurs after violent spasms and other nervous 

 symptoms, and the body quickly becomes decomposed. 



Family V. Vijjerina. Upper jaw with a single large perfo- 

 rate tooth on each side. Head cordate or trigonal, broader than 

 trunk. 



Crotalus L. Pit between the nostrils and eyes on each side. 

 Trunk and tail scaly above, scutate below, with all or most of the 

 subcaudal scutes simple (unpaired). Rattle composed of horny 

 rings, different in number, at the end of tail. 



Rattlesnake, Klapperschlange, Serpent a sonnettes, &c. The rattle consists 

 of horny pieces varying in number with the age of the individual. The 

 last (3 — 8) vertebrae of the animal coalesce to form a terminal bone of 

 a compressed conical form. This is covered by muscle and skin. The skin 

 is here thick and spongy, and has the general conical form of the bone 

 belov/ it, but has also two deep annular grooves which divide it into three 

 transverse swellings, decreasing in size from before backward. This skin 

 secretes the pieces of the rattle in succession. In adult animals the rattle 

 may consist of 20 — 30 hollow horny joints. The joints decrease in size 

 from the base to the extremity of the rattle, each joint the farthest succes- 

 sively from the end having been secreted at a period when the secreting 

 surface was larger. The pieces hang loosely but securely together, the 

 basal ring of one joint grasping the projecting second ring of the preceding 

 joint, and this again inclosing the third ring of the joint next but one pre- 

 ceding. Since the second rounded annular portion of each joint is thus 

 securely grasped by the first rounded annular portion of the piece behind 

 it, and the third by the second, and yet all of them so loosely as to leave 

 room for motion, it has been supposed that when the uppermost piece has 

 been completed and a new piece above this is about to be form;d, the skin 

 which is to secrete it is so modified that its first swelling which secreted 

 the first projection of the former piece assumes that shape and size which 



Cantor, Proceedings of Zool. Society, 1838, p. 75. 

 Haklan, Medical and Physical Researches, p. 501, quoted by Cantor. 



17—2 



