Tissue Membrane

Between every two dhatus there is a membranous structure called dhatu dhara kala, which separates one tissue from another. Within this specialized membrane, the dhatu agni along with ojas, tejas, and prana govern the functions of the particular dhatu. Each srotas (channel) is made up of its own related dhatu tissue, and the kala houses the agni that drives the transformation and nourishment of that tissue.

Dhatu dhara kala is the membranous structure that holds each dhatu. Dhara means holding and kala means membranous structure. One function of kala is to separate two tissues from one another, giving them distinct form. Kala is described as the mother of the dhatu because it holds and nourishes it.

The dhatu agnis are present within the kala and transform raw, unprocessed dhatu into processed, formed tissue. Each dhatu has its own kala and agni — for example, rasa dhatu has rasa dhara kala and rasa dhatu agni, rakta dhatu has rakta dhara kala and rakta dhatu agni, and so on. Within the kala of each dhatu there is also dhatu ojas, dhatu tejas, and dhatu prana, which maintain the function of the kala. On one side of the kala lies asthayi dhatu (unprocessed), which kala helps transform into sthayi dhatu (processed) through its dhatu agni, ojas, tejas, and prana.