312 



having fourteen rattles,* was killed, and I made a dissection of 

 its mouth in order to learn some details of the anatomical rela- 

 tions of the fangs and poison-apparatus. As the opportunity for 

 the study of the progressive development of these was an unusu- 

 ally good one, I will give the results somewhat in detail. 



The two fangs in use, with the poison-sacs at their base, pre- 

 sented nothing remarkable, excepting that they were old and 

 worn, and evidently soon to be shed. But directly behind these 

 the mucous membrane on each side was crowded with what may 

 be called the fangs of reserve ; for, like successive teeth else- 

 where, they are ready for complete development in turn, as fast 

 as those in use pass away. 



These were of all sizes from near that of the fangs in use, 

 down to the smallest germ, and I was able to easily count twelve 

 on each side. Their development I studied with the microscope, 

 and it appeared as follows : — First, a minute involution of the 

 mucous membrane (the tooth follicle^ ; in this is seen a small 

 conical papilla as the first trace of the future fang. This is 

 gradually developed by the aggregation of cells, and when about 

 one twenty-fifth of an inch in length, its cavity (the pulp-cavity) 

 is occupied by a net-work of blood-vessels. The growth after 

 this is more rapid and determinate. The epithelial cells covering 

 the apex of the papilla become lineally arranged, and, fusing 

 together, form fibres, which, when filled with calcareous salts, 

 constitute the intimate structure of the enamel. This enamel is 

 formed very early, and sometime before the appearance of the 

 dentine or ivory ; so that at one period is found simply the 

 epithelial tooth-sac crowned with a point of enamel. As the 

 tooth-sac increases and is pushed out, the enamel point is more 

 and more elongated, and becomes, finally, very long and acicular, 

 and with the sharpness well known in the perfect fang. Mean- 

 while the dentine, or ivory, is formed, and as this process is 

 going on, its edges begin to roll towards each other on the con- 

 vex and upper surface of the tooth. This rolling of the edges to 



* The popular belief is that the number of rattles on the tail indicates the num- 

 ber of years of the snake's life. But according to several observers (Bachman, 

 Holbrook, and Bearing) this is not so; for, not only may it lose several of the 

 rattles by accident, but two and even four have been known to form in a single 

 year. One of my own accidentally lost two of its rattles, and it is rare to find 

 specimens having more than ten or twelve. 



