The perimammary subcutaneous tissue is infiltrated, œdematous, painful on palpation and preserves the imprint of the finger. The teat is tense, swollen, very tender, and of reddish colour. In the grave forms the swelling extends forwards under the abdomen in the direction of the umbilicus, and backwards towards the perineum. The local temperature is abnormally high, the secretion of milk in the diseased gland is modified or checked, and sometimes this phenomenon extends by reflex action to the neighbouring quarters, although the latter may not themselves be affected. The inflammation rarely extends from one quarter to another, because the lymphatic plexuses do not anastomose (Fig. 237).
The animals lose appetite and fall away rapidly.
Resolution may occur after from five to eight days. By degrees all the symptoms then become less marked. The appetite returns, pain diminishes, the fever drops, and the lesions gradually disappear, but the yield of milk rarely regains its former amount.
Suppuration may occur; sometimes a superficial subcutaneous abscess forms, more rarely, a deep-seated, interstitial abscess, originating in the connective tissue or lymphatic spaces. With a superficial abscess, the local symptoms again revive to a slight extent; these are present in a more marked degree where the abscess is deep-seated. An extremely sensitive œdematous swelling forms, the skin covering which is at some point of a deep-red tint, whilst fluctuation gradually appears.
In cases of deep-seated abscess formation the general condition becomes alarming; the affected quarter is tense throughout, hard and very sensitive.
Deep-seated suppuration is difficult to detect, and exploratory punctures with a fine needle may be necessary before the diagnosis can be made.
Local or diffuse gangrene forms a rare complication. It is due to the vessels of one or several glandular lobules becoming obliterated or thrombosed.
Such a termination is indicated by extreme aggravation of the general symptoms, feebleness of the heart and great weakness of the patients, who fall into a condition of coma. Locally the udder remains œdematous, the skin becomes of a blackish-violet colour, whilst the local temperature falls and the animals die from exhaustion and intoxication.
Parenchymatous Mammitis.—Parenchymatous mammitis when mild is also termed catarrhal mammitis. It is in reality true primary mammitis; interstitial being primarily and practically perimammary lymphangitis.
In this case infection occurs through the teat, and may be localised in the sinus or excretory apparatus, giving rise to galactophoritis, but it usually extends to the acini. Inflammation of the mammary tissue is therefore direct and primary. It rapidly extends, however, through the glandular wall into the interstitial tissue, thus setting up (from the anatomo-pathological standpoint) a mixed mammitis. Clinical distinction between this form and interstitial mammitis is at first easy.