900 16. CROTALIDA 
The severity of the symptoms which follow a snake 
bite vary with the nature of the poison, the amount of the 
poison, the size of the person or animal bitten, and the rapid- 
ity with which the poison enters the circulating blood. 
The nature of the poison varies with the kind of snake. 
In western North America, however, Coral Snakes are small 
and quite rare and occur only in Sonora, Arizona and south- 
ern Utah. Practically, our only dangerous snakes are the 
rattlesnakes. 
The amount of poison thrown into the wound depends 
on a number of factors. Among these are the size of the 
snake, its activity at the time, its condition of health and 
nourishment, the condition of its fangs and whether both 
cause wounds, the extent to which the snake has depleted its 
supply of venom by recent use of its poison apparatus, and 
the protection afforded by clothing, hair, or the resistance 
of the part bitten. 
With any given quantity of venom thrown into the wound 
the relative size of the dose depends, of course, on the 
weight of the victim. Therefore, the danger is greatest 
when small children are bitten. 
The rapidity with which the poison enters the circulating 
blood is perhaps the most important factor of all. If it so 
happened that the fang entered a vein and the venom was 
thrown directly into the blood, dangerous or fatal effects 
would follow almost immediately. Fortunately, this almost 
never occurs. Usually the venom is injected into the sub- 
cutaneous tissues, and whether its entrance into the blood is 
rapid or slow depends largely upon whether the bitten part 
is richly or poorly supplied with blood vessels. Ordinarily 
some minutes elapse before the onset of symptoms. 
The pain and swelling which follow the bite of a rattle- 
snake often are very great, and later a blackish or purplish 
discoloration of the skin about the wound appears, as a re- 
