The fact that in Argentina, just as in France, strongyles have always been discovered in epizootics of this nature of itself constitutes something; and causes the second fact, that it has never yet been proved that any heavy mortality occurred in the absence of parasitic infestation, to assume considerable importance. Moussu regards these two facts as the greatest obstacles to Lignières’ theory. He states that in his view the verminous affection is the essential, primordial and primitive affection, and that microbic infection is only secondary, and an almost inevitable result of grave verminous infestation. It is quite certainly wrong to think that verminous affections may continue with scarcely any injury to the animal, especially when such a belief is based on observation of a few parasites which are not of a predatory character. In most cases of the kind now under consideration, the various parasites found (_Strongylus circumcinctus_ and _filicolis_, _Anchylostomes_, etc.) cause more or less grave lesions. These intestinal wounds facilitate the infection to which the fatal course of the disease is due. The disease, then, is not a special unvarying infection, but consists of multiple superposed infections. It is wrong to believe and to teach that the parasitic disease is of no importance, and Moussu declares his belief that the proposed vaccinations will prove unavailing. He is of opinion, on the other hand, that when the parasitic invasion can be overcome the mortality will be checked, and only those animals which are already suffering from severe infections will succumb. Is not this precisely what has been observed in human pathology regarding miners’ anæmia or miners’ worm disease (anchylostomiasis)? =The diagnosis= presents no difficulty for those who have had a little practice with the microscope, since the presence of eggs of the parasite can always be detected in the fæces in cases where external signs have given rise to suspicion of gastro-entestinal strongylosis. The macroscopic diagnosis on post-mortem examination is not so easy as might be supposed, and when very small varieties are in question it is sometimes necessary to examine the mucous membrane of the abomasum or intestine very carefully in order to discover the parasite. =The prognosis= is grave, because before attention has been drawn to many patients, the entire herd may be more or less infested. It is also grave because the pastures are infested with eggs or embryos, and the power of increase of these parasites is enormous. =Treatment.= The earliest and most energetic means should be adopted in all cases. Treatment comprises:— Drainage of swampy pastures. Dressing of the pastures with chemical manures, preferably with iron sulphate, at the rate of 40 to 80 lbs. per acre. Disinfection of manure to destroy the contained eggs or embryos. The use of chalk, iron sulphate, various acids, etc.