The clinical features resulting from the injection of the venom vary directly in intensity with the amount of the poison introduced, and the rapidity with which it reaches the circulating blood, being most marked when it immediately enters a large vein.  The poison is innocuous when taken into the stomach.

Locally the snake inflicts a double wound, passing vertically into the subcutaneous tissue; the edges of the punctures are ecchymosed, and the adjacent vessels the seat of thrombosis.  Immediately there is intense pain, and considerable swelling with congestion, which tends to spread towards the trunk.  Extensive gangrene may ensue.  There is no special involvement of the lymphatics.

The general symptoms may come on at once if the snake is a particularly venomous one, or not for some hours if less virulent.  In the majority of viper or adder bites the constitutional disturbance is slight and transient, if it appears at all.  Snake-bites in children are particularly dangerous.

The patient’s condition is one of profound shock with faintness, giddiness, dimness of sight, and a feeling of great terror.  The pupils dilate, the skin becomes moist with a clammy sweat, and nausea with vomiting, sometimes of blood, ensues.  High fever, cramps, loss of sensation, haematuria, and melaena are among the other symptoms that may be present.  The pulse becomes feeble and rapid, the respiratory nerve centres are profoundly depressed, and delirium followed by coma usually precedes the fatal issue, which may take place in from five to forty-eight hours.  If the patient survives for two days the prognosis is favourable.

Treatment.—­A broad ligature should be tied tightly round the limb above the seat of infection, to prevent the poison passing into the general circulation, and bleeding from the wound should be encouraged.  The application of an elastic bandage from above downward to empty the blood out of the infected portion of the limb has been recommended.  The whole of the bite should at once be excised, and crystals of permanganate of potash rubbed into the wound until it is black, or peroxide of hydrogen applied with the object of destroying the poison by oxidation.

The general treatment consists in free stimulation with whisky, brandy, ammonia, digitalis, etc.  Hypodermic injections of strychnin in doses sufficiently large to produce a slight degree of poisoning by the drug are particularly useful.  The most rational treatment, when it is available, is the use of the antivenin introduced by Fraser and Calmette.

CHAPTER VIII

TUBERCULOSIS

Tubercle bacillus—­Methods of infection—­Inherited and acquired
    predisposition—­Relationship of tuberculosis to injury—­Human and
    bovine tuberculosis—­Action of the bacillus upon the
    tissues—­Tuberculous granulation tissue—­Natural cure—­Recrudescence
    of the disease—­THE TUBERCULOUS ABSCESS—­Contents and wall of the
    abscess—­Tuberculous sinuses.