In more benign cases the synovial exudate from the joint cavities is simply cloudy, contains no infectious germs, and proves sterile on attempts at cultivation. In such cases there is no abscess formation. But most frequently this stage of serous exudation is only temporary, and the articular fluid, which at first seems sterile, may, when tested some days later by means of cultures, reveal the presence of organisms. The synovia accumulated within the joint sometimes contains fibrinous flocculi, which are at first small, but later form veritable coagula, filling up and thickly coating all the prominences of the joint and moulding themselves on the extremities of the bones constituting the articulation. Sometimes the cartilages undergo very rapid ulceration, the subjacent layers of bone become inflamed, and the osteoarthritis which develops is so severe and painful that the patients are forced to remain absolutely still, and are quite incapable of rising. The lesions may remain stationary at this point. In other cases suppuration occurs in the articulation itself, the wall of the synovial cavity, the periarticular tissues, and the skin soften; then the abscess breaks, giving rise to open suppurating arthritis. Animals are rarely kept long enough to become so gravely affected; many die before this stage, and the others are usually slaughtered. Moreover, they rapidly perish from exhaustion and from visceral complications of a pyæmic character. [Illustration: $1] In many cases post-mortem examination reveals nothing whatever in the region of the umbilical cord (through which infection has occurred), but the germs of infection may be found in the blood or general circulation; or again, careful investigation may show ulceration of the umbilicus, lesions of omphalitis, of ascending umbilical arteritis in consequence of infection of the thrombus, of umbilical phlebitis, or of infective peritonitis, etc. The infectious agent reaches the liver through the blood-vessels, then attains the posterior vena cava, after which the infection assumes the gravest possible character, producing complications like arthritis and purulent infection, with the formation of multiple abscesses in the depths of the viscera. The _Staphylococcus aureus_ and various streptococci are the most frequent but not the only causes of these infections. =The diagnosis= is not difficult, provided the disease be not mistaken for true rheumatism. As true rheumatism is very rare in young animals, and as, on the other hand, attention is aroused by the presence of lesions of the umbilicus and by the existence of diarrhœic enteritis, rachitis, etc., there is seldom room for doubt. =Prognosis.= The prognosis is extremely grave whenever the case results from infection of the umbilicus. French statistics place the mortality at 90 per cent. and German at 75 per cent.