Knowledge of Liquid Substances (Drava-dravaya Adhyaya) After the chapter Prevention of disease , (Roganutpadaniya) Acharya Vagbhata expounded the chapter Knowledge of Liquid Substances (Drava-Dravaya Adhyaya), said Lord Atreya and other great sages. In the previous three chapters, preventive measures to maintain positive health have been detailed. The present chapter deals with the liquid substances available in nature, and their properties have been described. All the liquid substances have been grouped as under: Water (Jala varga) Milk (Ksira varga) Sugarcane (Iksu varga) Honey (Madhu varga) Oils (Taila varga) Alcohols (Madya varga) Urine (Mutra varga) etc. Group of different types of water (Jala varga) Classification of water: According to nature, water is of 2 types: Rainwater (Pure) (Gangambu) Rainwater contaminated by dust and poison (Samudrodaka.) According to processing, it is of 5 types: Kevala Pakwa Ushna. Sausadha Ama According to th...