The interstitial ground substance plays an essential role in the physiological processes of the capillary and the cell. Together they form a fundamental unit of function in which the cell is the most important part. Therefore the fundamental unit is called: THE CELLULAR UNIT. It is proposed central role and that this enzyme is indispensible for normal healthy cells as well as for the reactive mechanism in critical situations. The reactive mechanisms can be divided into a local reactive mechanism and a general reactive mechanism. The local reactive mechanism has a function of RESTORATION. The general reactive mechanism is especially for PROTECTION AGAINST ISCHAEMIA and REDISTRIBUTION OF TOTAL BODY NUTRIENTS in order to stimulate the restoration. These two mechanisms may have important clinical consequences.