in other organs, laminitis, rheumatism. Treatment, adapted to strength of subject and type of disease, hygienic, anti-rigor, antiphlogistic, expectant, stimulant, antipyretic, febrifuge, sedative, moist compresses, derivatives, laxatives. In subacute form tonics, heart stimulants, febrifuge. In chronic cases add rich digestible diet, and easy open air life. This consists in inflammation of the spongy tissue of the lung involving mainly and primarily the walls of the alveoli and interlobular connective tissue with their respective trophic centres (nuclei). The acute congestion of excessive heart action and debilitated pulmonary capillaries described above, is primarily a disease of the bloodvessels which become over distended and may or may not lead to the inflammatory processes in their walls and the tissues adjacent. Pneumonia on the other hand is essentially inflammation of these tissues and nuclei, with exudation usually of a fibrinous material into their substance. PREDISPOSING CAUSES. =1.= =Age.= A very early age is nearly exempt, and from 6 years upward there are fewer cases relative to the equine population, variations that may be better accounted for by stabling, training and acquired immunity than by the mere fact of age. Of 237 cases, 2 were 3½ years; 32 were 4 years; 19 were 5 years; 131 were 6 to 11 years; 46 were over 11 years; and 7 of uncertain age (Trasbot). =2.= =Sex.= No visible effect. =3.= =Stabling, training, change of food.= While the young colt at pasture is practically immune, the period of stabling, transition to a dry and grain diet, and to the nervous excitement attendant on training and unwonted work as shown in the statistics of Percivall and Trasbot determine an enormous increase of cases. In a cavalry regiment Percivall found that 56.6 per cent. of all lung diseases occurred before the 5th year, and Trasbot found that at the Alfort Veterinary College 13.5 per cent. of all equine pneumonias occurred in the 4th year. =4.= =Hot Stables.= =Impure Air.= These two conditions usually coexist and prove potent causes especially in young horses brought from the fields. We cannot, however, separate this cause as usually observed from the action of pathogenic germs which are preserved and concentrated in such places. =5.= =Poor Health.= Debilitating diseases, insufficient and poor diet, overwork, exposure to cold draughts or darkness and any other cause which lowers the vitality predisposes. =6.= =A Previous Attack.= This usually leaves some structural or functional change which renders the lung more susceptible to a subsequent invasion. Against this must be placed the immunity which follows the contagious forms, but as this is usually exhausted in the course of six months it does not invalidate the position that the permanent impairment of pulmonary integrity is a predisposing cause. =7.= =Plethora.= Tending as this does to congestion it must be accepted also for the next pathological step—pneumonia.