As a general rule, in the case of a healthy man, Koch's lymph would not develop any reaction, its effects manifesting themselves in a febrile congestion, which betrays the presence of tubercles. In our pathogeneses (those of Mersch-Arnulphy), we note the following symptoms--"catarrhal pneumonia with soft hepatisation, and tendency to abscess formation; at post-mortems it is not a gelatinous or fibrinous exudation which oozes out from the alveoli, but an opaque and watery fluid; 'never,' so says Virchow, 'is there found the characteristic lesion of croupous pneumonia.'" A pneumonia from which issues an aqueous and opaque liquid! I confess I do not understand it. Experimentally this same lymph of Koch gives symptoms of inflammation of the arteries which are not found in clinical tuberculosis. Animals inoculated with progressive doses of _Avian tuberculin_, or with serum of tuberculous animals, undergo wasting and loss of appetite, and other general symptoms. They may die of cachexia, or may develop an isolated abscess; but they do not present characteristic symptoms as they would under the action of _Cantharis_, of _Phosphorus_, or of _Lead_. Finally, inoculation with dead bacilli may produce real tuberculosis. In the pathogenesy put forth by homoeopathists, pulmonary symptoms do not occupy a prominent place. Dr. Burnett, who has experimented on himself with _Bacillinum_, notes at the end of his symptoms, after the headache, a slight and almost insignificant cough. In explaining the clinical forms of infectious complaints, we are frequently forced to admit the increasingly preponderant part played by association of microbes--as it is the frequent case in diphtheria--and especially the modifications which depend directly on the disposition of the organ attacked, and not upon the action of the microbe itself. An examination of the above considerations leads me to the following conclusions: 1. That the importance of the materia medica of the tubercular virtues ought not to be exaggerated. There are few characteristic symptoms to take off; it is more wise to guide oneself in the homoeopathic application of the therapeutics by the clinical symptoms of the evolution of the various tuberculosis, rather than by the intoxication produced by their active products, the _Tuberculins_. 2. Koch's lymph, _Bacillinum_ and _Avian tuberculin_ must be studied separately, clinically as well as experimentally. _Bacillinum_ presents symptoms very different from those of _Avian tuberculin_, and especially from those of Koch's lymph; and I intend to divide my remarks into three parts, corresponding to these three substances, which have actually become homoeopathic remedies. * * * * *