_Definition._ An infectious fever of solipeds, of a specially low or adynamic type, and with a tendency to localization on the respiratory or gastro-intestinal mucosa, on the eyes, lungs, pleura, heart, liver, kidneys, subcutaneous connective tissue, joints, fascia, or nervous system. This disease was long confounded with the _influenza_ of man and while compelled for the identification of the affection, to retain this name in combination with the qualification _equine_, yet we would prefer to discard it entirely as conveying the idea that the illness is caused by Pfeiffer’s bacillus, which it is not. The term _typhoid fever_ which is in common use in France, has been selected to convey the impression of its two prominent features of _hyperthermia_ and _stupor_. But it is open to the same objection for it has been long applied to a specific disease in man having its own bacillus which is not present in the _equine influenza_. _Septicæmia Hæmorrhagica_ which has been adopted more lately, however correct it may be as indicating the tendency of the local lesions has a generic meaning rather than a specific one, and requires much more qualification to correctly designate the disease. The term _adynamic catarrhal fever of solipeds_ has this recommendation, that it expresses the prostration and debility which is such a marked feature of the disease, its great tendency to become localized on mucous surfaces, and the genus of animals that prove its victims. A better designation is still desirable and may perhaps be reached, when the pathogenic microbe shall be demonstrated beyond question.