492 The Action of the Venom of Echis carinatus. 
pre-existent deterioration of the quality of the blood and the feebleness of 
the circulation. The venom has, moreover, no effect on the nerves or nerve 
terminals of voluntary muscle. The venom has no appreciable effect on 
skeletal muscle. The effects on the circulation are produced partly directly 
and partly indirectly. From the point of view of lethality, the indirect 
effects, due to blood changes, are the more important. 
When perfused through the frog’s heart, strong solutions bring about an 
increase in the rate, followed by arrest of the heart in systole, and weaker 
solutions also quicken the heart, but arrest it in diastole. The venom also 
renders the heart-wall permeable to the contained blood solution, an effect 
apparently due to separation of the cardiac muscle fibres. 
Solutions of the venom diminish the flow through the frog’s blood-vessels, 
when perfused through them; but this effect is due, not to a direct con- 
stricting action on the vessels, but to the production, by the hemorrhagin 
contained in the venom, of an intense cedema of the tissues of the frog. 
In mammals, even very small doses of the venom injected intravenously 
may rapidly arrest the circulation by the production of intravascular 
clotting. If intravascular clotting be prevented, the venom produces a fall 
of blood-pressure, due partly to slowing, but mainly to weakening, of the 
heart’s contractions. 
Echis venom has no appreciable effect on the lymph hearts of the frog. 
The toxic effects of the venom are due chiefly to the production of alterations 
in the quality of the blood, of which the following are the most important :— 
Especially with lethal doses, there occurs a great reduction in the number of 
the red blood corpuscles in the circulating blood, which is due chiefly to 
hemorrhages, but, in the case of large intravenous doses, is due also to 
a small amount of hemolysis. The number of the leucocytes is usually 
considerably increased for some days after subcutaneous injection. The 
hemolytic action of the venom is unimportant in producing its lethal 
effects, and death frequently occurs without any hemolysis. The venom has 
a moderate hemolytic action on the blood zm vitro. Positive and negative 
phases of blood coagulability are produced by Echis venom in a manner 
similar to that which has already been described in the case of several 
venoms. 
Echis venom exerts little, if any, direct action on the respiratory centre or 
on the terminations of the phrenic nerves. Non-lethal doses of the venom 
produce a rise of temperature; lethal doses a rise, followed by a fall, of 
temperature. Lethal doses cause a diminution in the total quantity of urine 
secreted, and produce albuminuria, and, frequently, hematuria. 
