Under the head of infectious rheumatism or pseudo-rheumatism may be grouped joint diseases of a rheumatic type accompanying various general or local diseases in young animals and adults: diseases of the umbilicus, rachitis, peripneumonia, retention of the fœtus, dysentery, etc. These diseases are characterised by articular symptoms, which sometimes appear early, sometimes only when the disease itself is declining, and develop suddenly or gradually, the joint cavities themselves either being directly invaded by the agents of the primary disease or remaining exempt. These pseudo-rheumatic attacks are due to the localised action of microbic toxins on the articular synovial membranes. Sometimes the serous membranes of the large body cavities are also implicated. This theory explains the development of acute arthritis without the presence of gonococci during the course of an attack of blenorrhagia in man, and may be applied in respect of certain forms of arthritis or synovitis without the presence of microbes in domestic animals. INFECTIOUS RHEUMATISM IN YOUNG ANIMALS. =Causation.= To explain the occurrence of infectious rheumatism in young animals a variety of causes has been invoked, such as bad feeding, the absence of that purgation which usually follows the action of the mother’s first milk (_i.e._, colostrum), and clears the bowel of meconium, the effect of heredity, of chills, of insufficient food, and of unduly abundant or very rich food, which has been said to produce indigestion and its various complications. All these causes may play a certain part in favouring the development of infectious rheumatism, but none constitutes the direct cause.