This section is from the book "The Sushruta Samhita", by Kaviraj Kunja Lal Bhishagratna. Also available from Amazon: The Sushruta Samhita.
Having laid himself prostrate at the feet of the holy and wise Dhanvantari, the master of all the S'ástras, Sus'ruta addressed him as follows: - "Enlighten and illumineus, O Lord, on the number and classification of snakes, on the nature of their poison and on the distinguishing marks of their respective bites", whereupon Dhanvantari, the foremost of all physicians replied as follows: - Innumerable are the families of serpents, of which Takshaka and Vásuki are the foremost and the most renowned. These are supposed to carry the earth * with the oceans, mountains and the islands on their heads and are as powerful and furious as the blazing fire, fed upon the libations of clarified butter. I make obeisance to those who constantly roar, bring down rain, scorch the whole world (with the heat of their hundred-headed venom) and are capable of destroying the universe with their angry looks and poisonous breath. It is fruitless, O Sus'ruta, to enter into a discourse on the treatment of their bites as they are beyond the curative virtues of all terrestrial remedies. 2-A.
I shall, however, describe in due order, the classification of the terrestrial snakes whose poison lies in their fangs wherewith they bite the human beings (and other animals). They are eighty in number, classified into five main genera, namely, the Darvi-kara (hooded), Mandali (hoodless and painted with circular patches or rings of varied colours on their skin), Rájimán (hoodless and striped), Nirvisha (non-venomous or slightly venomous) and Vaikaranja (hybrid species). The last named is also, in its turn, divided into three sub-divisions only, viz., the Darvi-kara (hooded), the Mandali (hoodless and ring-marked) and the Rájiman (striped ones). 2.
* In the Hindu mythology the earth is supposed to rest on the heads of snakes, the inmates of the infernal region.
Of these there are twenty six kinds of Darvi-kara snakes, twenty-two of the Mandali species, ten of the Ráji-man class, twelve of the Nirvisha (non-venomous) species and three of the Vaikaranja (hybrid) species. Snakes born of Vaikaranja parents are of variegated colours (Chitra) and are of seven different species (three of these being Mandali (marked with rings) and (four) Rajila (marked with stripes). 3.
A snake trampled under foot, or in a fit of anger or hunger, or anywise terrified or attacked, or out of its innate malicious nature, will bite a man or an animal. The bites of these snakes highly enraged as they are, are grouped under three heads by men conversant with their nature, viz., Sarpita (deep-punctured), Radita (superficially punctured) and Nirvisha (non-venomous) bites. Some of the authorities on snake-bites,however, add a fourth kind viz., Sarpangabhihata (coming in contact with the body of a serpent). 4.A.
The bite in which one, two or more marks (punctures) of fangs of considerable depth are found on the affected part attended with a slight bleeding as well as those which are extremely slender and owe their origin to the turning aside and lowering of its mouth (head) immediately after the bite and are attended with swelling and the characteristic changes (in the system of the victim) should be known as the Sarpita bite. A (superficial) puncture (or punctures) made by the fangs of a snake and the affected part being attended with reddish, bluish, whitish or yellowish lines or stripes is called the Radita bite, which is characterised by the presence of a very small quantity of venom in the punctured wound. A Nirvisha (non-venomous) bite is marked by the presence of one or more fang marks, an absence of swelling and the presence of slightly vitiated blood at the spot and is not attended with any change in the normal (physiological) condition of the person bitten. The contact of a snake with the body of a naturally timid person may cause the aggravation of his bodily Váyu and produce a swelling of the part. Such a man is said to be Sarpángábhihata * (affected by the touch of a snake). 4.
A bite by a diseased or agitated snake or by an extremely old or young one, should be considered as considerably less venomous. The poison of a snake is inoperative in a country resorted to by the celestial Garuda (the king of birds;, or by the gods, Yakshas, Siddhas and Brahmarshis, as well as in one in which there are drugs of anti-venomous virtues. 5.
 
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