The first is a threadlike worm, pointed at both extremities, and from ½ to 1 inch in length. It exhibits a red tint, which zoologists refer to the presence of blood in its digestive apparatus, derived from the host’s intestinal mucous membrane. Some doubt has been thrown on the nature of this coloration, however; and certain Italian authors, in common with Lignières, have declared it due to a certain red pigment developed in the tissues of the parasite, the spectroscopic reaction of which differs from that of hæmoglobin. The strongyles are said not to penetrate the mucous membrane, but simply live on the intestinal contents. This may be true of certain varieties, but it is none the less certain that others penetrate the mucous membrane deeply, even to the extent of becoming half-embedded in it. Particularly is this the case with _Strongylus circumcinctus_, found in the epizooty which occurred at Grignon, and also found by Moussu in grave epizooties which he has from time to time investigated. According to Lignières this gastro-intestinal strongylosis only plays a trifling part in the development of the above-mentioned disease, which he declares to be due to infection with a cocco-bacillus of the Pasteurella group, the development of which alone, he states, explains all the symptoms. In France the disease now under consideration has never extended beyond limited regions, but in Argentina, where Lignières carried out his investigations, it is said to be very fatal. Lignières bases his opinion on the following facts:— Firstly, that experimental verminous infection of young animals does not produce either anæmia or cachexia. Secondly, that animals in excellent condition may prove to be infested with large numbers of parasites. Thirdly, that animals which have succumbed to this disease, hitherto regarded as verminous, sometimes prove to harbour few or no parasites. Fourthly, that this grave and fatal disease, and the symptoms by which it is clinically recognised, can be produced with cultures of the cocco-bacillus, which he has isolated. These statements are very precise, but Moussu declares that he has never yet been convinced of the reliability of the last statement referring to experimental transmission, any more than of the data regarding alleged protective vaccination. =The symptoms= of gastro-intestinal strongylosis or ovine pasteurellosis point to a progressive pernicious anæmia of chronic or subacute form. Rapidly progressive cases are exceptional. In France the form seen is almost invariably chronic. The animals appear dull, sluggish, and feeble; they lose appetite, waste, become anæmic, then cachectic, and, after several months, die of exhaustion and wasting, after having shown diarrhœa during the later stages. The fæces are pasty, and exhale a very marked putrefactive odour. There is little room to doubt that auto-intoxication from resorption of intestinal products is continually going on.