1st. Clip the animal close to the skin to allow of careful examination. In some affections, this may be dispensed with, but as a rule it should be followed. What appears to be a circumscribed eruption may be shown to be general, or at least extensively diffused over different regions. Or what was shown only by scurf or scab may be seen in its earlier and more characteristic stage as erythema, papule or vesicle. It may even be desirable to shave the affected part, care being taken, not to slice off the characteristic papules, etc.
2d. Make the examination in a clear day in full sunshine if possible. In dark, cloudy weather, and in dimly lighted stables it is impossible to identify the different lesions. Artificial light is very unsatisfactory. Warmth, as in sunshine, or in a warm day or room, increases any itching and the cutaneous circulation and congestion, and renders more lively and active the animal parasites that may be present. These may be found in the surface scrapings taken in warmth, and not at all if taken in cold. A hand lens will assist in the discovery of the larger parasites, while for the smaller ones the microscope must be employed.
3d. Examine carefully all parts of the skin and even the visible mucosæ, estimating whether any lesions of the latter indicate extension from the skin, by proximity, or a general constitutional affection. Scrutinize particularly such parts as have not been abraded by mechanical injury—those which show the primary character of the lesion. Is the affected portion of the skin dry or moist? Some eruptions like impetigo or grease are always moist, others like pityriasis or dry eczema are habitually dry apart from mechanical injuries. Ascertain the color, odor and consistency of any discharge. It may be a limpid or reddish serum in grease, honey like in impetigo, oily in farcy, greasy in swine plague. The odor is fœtid in grease, canker and thrush of the frog, cheesy in variola, and mousy in favus.
4th. To learn the true nature of the eruption a warm, soapy wash may be essential to remove scurf, scab, and other encrustations.
5th. Note the depth and extent of the skin lesions, the thickening of the skin, its pliancy or rigidity, its adhesions to subjacent parts or free movement upon them, whether it is contracted into folds or ridges, the degree of congestion, the nature of the eruption, uniform congestive redness, papule, vesicle, pustule, squama, sore, ulcer, nodule, slough, etc. Are the individual lesions isolated or confluent?
6th. The presence of itching and its degree are important data. Pruritus is always excessive in ordinary acariasis, marked in eczema, phthiriasis, and some neuroses, and very slight in a number of skin affections (pityriasis, ringworm, grease, thrush, contagious acne). The abrasions and sores caused by rubbing, scratching, etc., will usually give a key to the degree of pruritus, and handling the part will render the condition evident.
7th. The history of the case is always important. Is it chronic or acute? Continuous or intermittent? Associated with any special conditions of proximity to other diseased animals, to special feeding, watering, exposure, housing, harnessing, driving, which might account for it? Did there coincide with its eruption any indigestion, gastric or intestinal, or any hepatic, urinary or nervous disorder on which it might be dependent?
Prognosis. This is subordinate to the nature, causes, course, duration and complications of the disease.
Microbian dermatosis (variola, aphthous fever, rouget) usually follows a rapid course and recovery is perfect with some measure of immunity.
Parasitic dermatosis (acariasis, phthiriasis) is liable to have serious secondary results (infection to man or animals, loss of wool, tender skin), and to run a chronic course.