It must be remarked that the organs we have studied are essentially reducers, and that the more powerful reducers yield the most toxic extracts. We find here a confirmation of Armand Gautier's views regarding the anaerobic origin of the toxic substances formed within the organism.[87] [87] POZZI-ESCOT: _Compt. rend. de l'Acad. de Médecine_ (3), XLVII, p. 400. See also POZZI-ESCOT: _Etat actuel de nos Connaissances sur les Oxydases et les Réductases_. Dunod, publ., Paris. 1902. Blood serum precipitated by alcohol affords products which possess very marked toxic power. It would appear that the toxic products we speak of here are thermogenic diastatic substances derived from the white blood corpuscles. In certain diseases the blood serum may acquire a high degree of toxicity. We will recur again presently to this property as a normal characteristic of the blood of various animal species, and will study it in greater detail in a future volume of this collection, devoted to the immunizing active principles. =Glandular Secretions.=--On studying the venoms we will see that a certain number of these products are the result of glandular secretion. This is a general property of the glands; and it was Brown-Sequard who first drew attention to the rôle played by these glands, and to the importance of the products that they throw into the blood.[88] [88] _Compt. rend. de l'Acad. des Sciences_, CXIV, pp. 1237, 1318, 1399, and 1534; CXV, p. 375; and CXVI, p. 856. P. Noel showed later that the testicular juice possesses a high degree of activity, which he attributed to an oxidizing ferment, and which we have already mentioned, _spermine_. The greater number of the other glands contain proteid matters and various peptones, more or less toxic, with amides and alkaloids. Particular mention must be made of the thyroid gland, the secretions of which exercise a powerful action on the nervous centers and on nutrition.[89] It appears reasonable to attribute to the secretions of this gland a very powerful antitoxic action, and the first proof of this fact is that the organisms deprived of this gland become the seat of serious derangements; the urines of such organisms become particularly toxic, while, on the other hand, the hypodermic injections of the aqueous extract of the gland, when the derangements spoken of exist, cause the immediate disappearance of the derangements caused by the excision of the gland.[90] [89] LAULANIÉ: _Compt. rend. Soc. de Biol._, 1894, p. 187. [90] GLEY: _Compt. rend. Soc. de Biol._, 1891, p. 250. Attempts have been made to isolate the active principle of the glands. Notkine isolated a _tyroproteid_,[91] which is not sensibly toxic to animals who still retain the gland, but which becomes toxic when the gland is excised. It seems probable, however, that this product is not the principal agent of the thyroid gland. [91] _Semaine Médicale_, Apr. 3, 1895, p. 138.