_Causes._ This is most commonly seen in dogs, in which it may depend on house life with overfeeding on stimulating, spiced, albuminous food, compulsory restraint of urination and defecation in obedience to the demands of cleanliness, distended bladder, and rectum, constipation, proctitis, piles, and other sources of local irritation. In all animals its origin is favored by the formation or arrest of calculi in the prostate, the pelvic urethra or even the bladder; by drug strangury from cantharides or other irritant diuretic; by excess of urea, uric acid or other irritant in the urine; by infection extending from the urethra or bladder; by ulceration or stricture of the urethra; by rude or incautious catheterization, or injection; by exposure to cold; and by local infection in pyæmia and other general zymotic disorders. Most of these conditions conduce to local excitement and hyperæmia, which from adjacent organs, are sympathetically transferred to the prostate. The same is true of frequent, and intense generative excitement which according to Lafosse and Cadiot is a common cause of prostatitis in stud horses. Again the abscess of strangles may become localized in the prostate, or the nodule of glanders, or the tubercle of tuberculosis (cattle, pigs, dogs). Cadiot suggests that in animals, divested of the tail, external injuries to the perineum may extend by continuity to the prostate, as happens to man from horseback or bicycle riding. He adduces no cases however. The habit of masturbation acquired by certain males may also be adduced theoretically as both cause and consequence of prostatitis but future observation must show how frequently this really operates. _Forms. Lesions._ According to the nature of the lesions the affection has been divided into different forms 1st, =Follicular= or =Parenchymatous=; 2d, =Diffuse= or =Interstitial=; 3d, =Circumscribed Prostatic Abscess=; 4th, =Multiple Miliary Abscesses=. =Follicular Prostatitis= implicates primarily the follicles and gland ducts and finally the entire gland tissue. It is usually associated with and doubtless often proves an extension from an adjacent infective urethritis, and tends, in persistent cases, to go on to interstitial inflammation and abscess, or hypertrophy. This is characterized by more or less swelling of the prostate, with increased vascularity of its mucosa and the oozing from its openings and gland ducts under pressure, of a thick, yellow, gelatinoid fluid containing pus and granular epithelial cells and sometimes striæ of blood. =Diffuse= (=Interstitial=) =Prostatitis= shows, in addition to the general swelling and muco-purulent discharge, a considerable exudate into the interstitial tissue, with increased tension and resistance of its substance. It is associated during life with more fever and constitutional disturbance than the simple catarrhal or follicular form.