What is it in a man, asks Sushruta, that falls sick? What is that that we treat medicinally? The body or the mind? Sushruta says that, "anything that afflicts the inner man (self or Purusha) is disease‡; and that disease has its primary seat in the inner spring of vitality from which it flows out to the surface, the external body". In man, as in everything else in the universe, the direction of the inherent force is from the centre to the circumference. The shock is felt first at the centre of vitality, whence it is transmitted outwards and thus affects the energy which holds the molecules together, Dvyanuks and Tryanuks (Binary and tertiary atoms) of which the gross body is composed, and further opposes the dissolution of those molecules into their elemental constituents in the living organism. Even in cases of external injuries such as snakebite, etc. the potency of the virus is carried at once to that centre from whence it is almost instantaneously transmitted through the external channels of the body to its surface, otherwise what purpose does the Vayu (nerve force)serve in the human economy? What do those myriads of Chaitanya-vahini Nadis (sensory nerves) exist for in the human system? In all diseases the subjective sensations are the first to be experienced. "I am ill," "I feel hot," etc. are the voices of sensations, which form the "esse" of the disease. Disease then is a force and not matter.*
Patanjala Darshanam V'ibhutipada 29 - 30 A.
Patanjala Darshanam. Vibhutipada. 21. A.
Sushruta samhita. Sutra. Chap. I.
Sushruta, though adopting the Vedic pathological dictum of Tridhatu, has expressed a very clear opinion on the subject. He observes that the relation between a disease and the deranged Vayu (nerve force), Pittam (metabolism) and Kapham (unutilised product of the system), and the pathogenic factors which lie at the root of that disease, is not real but contingent. These morbific principles may permeate the whole organism without creating any discomfort, and it is only when they find a distinct lodgment, and are centred in some distinct part or tissue of the body, that they become the exciting factors of disease.
The next question which naturally arises in connection with such a theory of pathogeny, is what is medicine, or in other words, what is it in the drug that cures! Sushruta, after closely investigating all the theories on the subject, inclines towards the opinion that it is the potency of the drug that is curative, though he observes that inasmuch as potency cannot exist independently of a drug, a drug is of primary interest for all practical purposes in therapy.