In a variety of conditions the hairs split up and break, leading to bristling or baldness. In debilitated conditions, when the hair is badly nourished, in ringworm when it is invaded by a cryptogam, and in the various nodular or ringed conditions of the hair this brittleness and splitting appears. The term Trichorrhexis (rexis a bursting forth) has been applied to one of these affections, in which the hair swells and bursts into a number of filaments giving it a broom-like termination. Trofimo describes this as affecting two-thirds of the horses of an artillery brigade, and showing upon the back, croup, mane and tail in isolated patches. Megnin, Trasbot and Roy have observed similar cases. The affected hair a short distance from the skin swells into a grayish white nodule and breaks across, leaving a tuft of fine filaments. The patches look to the naked eye as if singed, but when the hair is magnified the difference is easily made out, as there may be several nodular enlargements on the same hair, and the brushlike spread of filaments at the broken end is entirely unlike the solid node on the end of a singed hair.
The causes of the affection have not been demonstrated, though indications point to an infection which gradually extends from the first point of attack. This extension is not limited to the area presided over by particular nerves, and there is no other indication of disordered innervation. Trasbot has seen the disease transmitted from horse to horse by the use in common of combs, brushes and rubbers, and in other cases experimentally by rubbing the scurf from a diseased animal on the skin of a healthy one. From observations on the human subject Montgomery looks on it as a result of extreme dryness and brittleness of the hair, and charges dry climates and seasons, and an abuse of soap in washing as conducive causes. Debility and impaired nutrition of the hair may operate in the same way. No specific microbe has been constantly found in these cases and until such factor can be proved, it may be held that among the etiological agents impaired nutrition and dry air are important.
In the way of treatment shaving of the affected parts and oily or vaseline applications may be tried, together with such slight cutaneous stimulants as petroleum, weak tincture of cantharides, sulphur, tar ointment, etc. Roy noticed that cases that had lasted all winter recovered after shedding of the coat. It might be assumed that the evulsion of the infected hair, and the vascular stimulus necessary to the new growth contributed to the result.
CONSTITUTIONAL DISEASES.
RHEUMATISM.
Definition. Past views. Causes: heredity, age, cold, damp, cold climates, seasons, exposure, buildings, cellars, night chills, weather vicissitudes, valleys, wading, checked perspiration, lactic acid, metabolic products, acid phosphate of soda, vegetable acids, neuropathic causation, infection, microbes, injuries, overwork. Lesions: in joints, synovia, serosa, articular cartilage, fibro-cartilage, articular lamella, bone, eburnation, ligaments, joints affected in horse and ox, blood changes, albumen, fibrine, blood globules, pericardium, endocarditis, valvular disease, myocarditis, embolisms in lungs, pleura, nervous lesions, digestive system.
Definition. A constitutional, inflammatory affection, probably toxic, tending to localization in the joints, muscles, tendons, fascia, skin, heart and serous membranes and with a marked disposition to shift from place to place.
The word is derived from rhein (γειν) to flow, and was originally employed to indicate that an acrid humor, generated in the brain or elsewhere escaped mainly by the nose and eyes as a catarrh. The idea naturally followed that the retention of this humor caused inflammation in the joints, muscles, heart or elsewhere. The connection of these various conditions with exposure to cold, led to the association of the name with the various internal inflammations in which chilling appeared to have been a factor, until it was difficult to limit it by any definite line. Finally infectious diseases implicating the joints or muscles (influenza, contagious pneumonia, omphalitis, gonorrhœal rheumatism), and diseases of metabolism (gout and possibly rheumatoid arthritis) have added to the general confusion.
General Causes. Heredity. This has been more definitely traced in man than in the lower animals, the line of family descent being more easily followed in man. Children of rheumatic parents are more obnoxious to the disease in the ratio of 5 to 1. In the absence of data for animals, we may say that it is probable that the influence of heredity will hold good for live stock in this matter. Whether the disease results from faulty metabolism or from microbian invasion or toxins, the hereditary defensive powers of the animal cell are likely to be an important factor.
Age. Genuine rheumatism is not common at a very early age, but in animals as in man, attacks especially those in the prime of life, accustomed to vigorous exercise, free perspiration and succeeding chills. There is as yet no direct evidence of an exhaustion of the susceptibility of early maturity and of any consequent immunity of the old.
Cold and damp. The association of rheumatism with cold and damp has always been so notorious that no argument is needed to enforce the truth. It is pre-eminently the disease of cold climates and cold situations exposed to the north and east in Europe, or to the north and west in North America on the Atlantic slope. It is very little prevalent in the tropics. Buildings and yards that lack sunshine and exposed storm-swept hillsides show cases most numerously. Dogs kept in cold, damp sunless cellars often suffer. Cold, damp or frosty nights start or aggravate cases in animals left out in the field, while warm sunshine usually brings immediate improvement. A sudden change of weather to cold and wet is the signal for aggravation of the existing disease, though this may have set in before the change of weather has been fully developed. Late autumn and early spring with their sudden changes, their sleet and rain are especially hurtful and particularly to chronic cases. The cold, raw ocean winds on the Pacific coast contrasting with the warm sunshine is a marked contributing cause. The currents of cold air that draw up through shaded valleys, gullies and ravines expose their denizens to attacks. Rheumatism is more rare among well housed and carefully treated family horses, and less so in draught, dray and other hard working horses that are made to cross streams and stand with feet and legs in cold water while the body is drenched with perspiration. Dogs suffer in the same way while hunting. Haycock attributes many attacks to washing the legs with ice cold water when the animal has just returned to the stable heated and perspiring. If then left undried and unbandaged in a cold draught these conditions are still farther aggravated. This was formerly attributed to the suppression of perspiration, but it occurs in an animal which has just perspired freely and is now in no special need of further elimination through the skin. It appears to be due rather to the action of the cold on the nerve endings, the susceptibility of which has been enhanced by the free secretion and general relaxation.