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reference to the circumstances which favour their invasion, the disturbance which they occasion, and the means of cure. BESIDES THE PARASITES belonging to nematodese, which have already been described as infesting the digestive canal of the horse, there are some others which are referred to by authors as of occasional occurrence. These have not been observed by veterinarians in this country, aud do not appear to be of sufficient importance to require any special notice. The different round worms have been described separately, but it is necessary to observe that the host may harbour more than one species at the same time. An extraordinary case is reported by Krause of a horse which was infested with 500 Ascaris megalocephala, 190 Oxyuris curvicula, 214 Sclerostoma armatum, and an immense number of Sclerostoma tetracanthum, in addition to some cestode worms, both mature and in the scolex stage. Such a state of parasitism must be taken as altogether out of the common course, and it is unfortnnate that there is no record of the animal's condition during life. Occasionally the respiratory tubes of the horse are invaded by a nematode worm, Strongylus micrurus. This form of parasitism is, however, rare ; indeed, only occurs when colts are grazing on pastures on which there are calves and lambs infested with strongles, and the parasites will be referred to in their proper place as they exist in the respiratory organs of ruminants. NEMATODE WORMS IN CATTLE AND SHEEP. Ruminating animals habitually harbour several varieties of round worms, some of which cause serious derangement. Of chief importance among them is the worm which invades the breathing tubes and lung tissues, inducing changes of structure which remain long after the worms have migrated from their habitat. The lung strongle, or lung worm, is well known to the stockowner, presenting the