Techniques for examination of the arteries, veins and lymphatics are described before detailed descriptions of the history and clinical features of diseases that affect them. Pressure necrosis causes thickening of the skin, a purple or blue discolouration, blistering, ulceration or patches of black, dead, gangrenous skin. The skin temperature can only be assessed reliably if both lower limbs have been exposed to the same ambient temperature for a full 5 minutes. Uncover the limbs and perform some other part of the physical examination to allow the skin temperature to adjust to the temperature of the surrounding air. Press on the pulp of a toe or finger for 2 seconds, release pressure and then observe the time taken for the blanched area to recover. This gives a crude indication of the rate of blood flow in the capillaries and the pressure within them. This time can be compared in both limbs.