BATRACHIANS AND REPTILES OF OHIO. 135 
Family:  CROTALIDAE. 
This family embraces all of our poisonous snakes. One 
character is present in them which is found in none of the non- 
poisonous snakes and hence is an excellent criterion by which one 
may tell poisonous from non-poisonous forms. Between the eye 
and the nostril (Fig. 1) on either side is a deep pit that is simply 
an infolded part of the skin in that region. The function of the 
pit is not known. It has, however, embedded in its walls, termini 
of nerves which would suggest that it was a sense-organ, of the 
same category, perhaps, as Leydig’s corpuscles. 
The fangs (Figs. 2 and 3) of the poisonous snakes are simply 
long, sharp teeth in the upper jaw, perforated with a tube (a’) 
that connects with the duct of the poison gland (a), the whole 
forming a hypodermic injection apparatus. The poison gland 
(a) lies above and posterior to the base of the fangs. Above and 
below it run two large muscles (4 and 7) which serve to compress 
the gland and force out the venom. Should a fang be broken off 
another stands ready to replace it, (Fig. 3.) In our poisonous 
snakes the fangs are borne on the maxillary bone, which is hinged 
so that the teeth may be folded back and drawn into a sheath. 
Giigt 2. 5/-) 
When disturbed these snakes throw themselves into a coil 
from which they strike at the intruder by suddenly straighten- 
ing the body. ‘They are not able, however, to strike more than 
half their length, so that a four-foot snake could strike but two 
feet from coil. 
All our venomous reptiles are sluggish and will strike only 
when annoyed. ‘The Rattle-snakes are provided with a series of 
chitinous ‘‘ rattles,’ which are simply modified scales. These 
grow on the end of the tail, being formed continuously. The 
first one formed in the young snake is known as the ‘‘ button,”’ 
it being smaller than the subsequent ones. The rattles are fre- 
quently broken off, as may well be supposed. The age of the 
animal hence, for this reason alone cannot be told from the num- 
ber of rattles even if one rattle were formed a year, which is by 
no means the case since they vary in their periods of growth. 
Thus, at times, two or more rattles may be formed within a 
twelve-month or but one. It may be said that a rattle is formed 
at each hedding of the skin. 
