The Traumatic type (Samghatha-vala-pravritta) includes diseases that are caused by an external blow or are due to wrestling with an antagonist of superior strength. They may be sub-divided into minor divisions, according as the disease is due to an external wound, or to the bite from any fierce beast or poisonous reptile, etc. These types belong to the Adhi-bhautikam type, i. e. (brought about by physical causes).
The Periodical type (Kala-vala-pravritta) includes diseases that are brought about by the variation of atmospheric heat or humidity with the change of the seasons, and admits of being grouped under two different sub-heads, according as the seasons, which usher these changes in, exhibit natural or contrary features.
The Providential (Daiva-vala-pravritta) type includes diseases that are the embodiments of curses, divine wrath or displeasure, or are brought about through the mystic potencies of charms and spells, as described in the Atharva-Veda. This type may be divided into two minor divisions according as the disease is due to such acts of God as when a man is struck by lightning, etc., or to the malignant influences of demons and monsters, and these may be further grouped under two main sub-heads, according as the disease assumes a contagious character (epidemic), or is purely accidental, and restricts itself to isolated cases (sporadic).
The Natural or the Spontaneous (Svabhava-vala-pravritta) type includes such natural organic phenomena as, decrepitude, death, * hunger, thirst, sleep, etc. These phenomena are either Kalakrita (timely) or Akalakrita (untimely). They are called Kalakrita when they occur at the proper time in persons who strictly observe the rules of health, and Akalakrita, when they appear at the improper time (morbid or premature) as the effects of unhealthy living. These diseases belong to the Providential or Adhi-daivikam type †. Thus we have classified diseases into their several types.
The deranged bodily humours such as, Vayu, Pittam and Kapham should be looked upon as the primary sources of all diseases, inasmuch as symptoms characteristic of each of them may be detected in the case of a disease of whatsoever type, (which usually abates with their corresponding subsidence), and also because the Shastras have ascribed to them the fatherhood of all maladies that assail the human frame.
* According to certain authorities "Death" may also mean death of tissues.
† Several authorities on the other hand include such diseases as thirst, hunger etc., within the Adhyatmika class inasmuch as they are but the indications of the want of certain vital principles in the body and appear in the mental plane (Adhyatmika) only as longings for water, food, etc but modifications of their own qualities, so the three fundamental bodify humours underlie at the root of, and run through, the course of all known forms of bodily distemper.