Mastitis is always due to the presence of microorganisms which in many cases gain access to the gland through fissures or abrasions by means of the lymphatics. In other instances the germs may be in the blood and a local stasis may encourage the infection. Still again, they seem to enter through the normal nipple openings. _Symptoms._—The parenchymatous inflammation begins with a chill, and the temperature promptly rises to 102° to 105° F. The pulse is high. The patient complains of headache and thirst. Examination reveals hard, tender nodules in some part of the gland. The skin may or may not be reddened. If the trouble has begun in the connective tissue, the skin will be diffusely reddened, the nodule ill-defined, the temperature will rise gradually and the chill may be absent. _Treatment._—The breast is put at rest. No tight binder is applied, no breast pump, no massage. No heat is allowable. Ice bags surround the gland night and day. The liquids by mouth are restricted and saline cathartics given. Codeine may be administered for pain. Usually the symptoms subside without suppuration in from one to two days. Should the inflammation persist for more than two or three days, in most cases the tissue will break down and form a _mammary abscess_. When it is evident that suppuration has begun, heat may be applied to the gland and the process accelerated. The abscess may be superficial or deep and will be diagnosed by a bogginess in a circumscribed area or by fluctuation. The abscess must be opened as soon as possible. The nurse sterilizes a bistoury and a pair of long artery forceps. Lysol solution and cotton sponges are made and sterile gauze for packing. The hands are surgically prepared and rubber gloves worn. If an anæsthetic is required, gas may be used, or chloroform. The incision is made radially from the nipple so as to minimize the injury to the milk ducts. A gauze drain may be required for a few days. In the _after-care_, the nurse must be scrupulously clean and not convey contagion from the breast to the woman’s genitals, to the child’s eyes, navel or vagina, nor to her own person. =Excess of milk= is rare, but may be observed for a short time after the glands fill. It seldom requires treatment, but saline cathartics, restriction of fluids, and putting the child on a four-hour schedule will reduce it. Pads may be worn if it runs away freely. =Scarcity of milk= is only too common. There may be enough at first and the quantity gradually diminish, or it may be deficient from the very beginning.