Antivenomous serum, in a dose of 0·01 or 0·05 c.c., neutralizes the bacteriolytic action of 1 milligramme of _Cobra_-venom, while normal serum heated, even in larger doses, is without effect. The lysin and the antivenomous serum appear also to enter into stable combination; by heating to 80° C., after dilution of the mixture neutral antivenomous serum + venom, the property of dissolving is not restored to the latter. Pursuing his researches upon the bacteriolytic actions, Noc has also shown that the _fresh_ serums of the rabbit, horse, guinea-pig, rat, and man are capable of destroying them completely. We must conclude from this that venom has the property of fixing the alexin of these fresh serums, and in fact it is easy to show that this fixation takes place by experimenting with hæmolytic alexin, which is much more easy to study; it is sufficient to eliminate the intervention of the hæmolysin proper to _Cobra_-venom. With this object, Noc employed horse-corpuscles (which are readily dissolved by fresh rat-serum), and neutralised the hæmolysin proper to the venom by antivenomous serum, which has no effect upon fresh horse-corpuscles and upon the alexin of rat-serum. For experimental purposes six tubes are prepared with contents as follows:-- (1) 0·5 c.c. of fresh rat-serum. (2) 0·5 c.c. of fresh rat-serum + 0·5 milligramme of Cobra-venom (0·5 c.c. of a solution of 1 in 1,000). (3) 0·5 c.c. of fresh rat-serum + 1 milligramme of venom (after fifteen minutes’ contact of the venom with the alexin in tubes 2 and 3 the venom is neutralised by 1 c.c. of antivenomous serum in the case of tube 2, and by 2 c.c. in that of tube 3). (4) 1 milligramme of venom. (5) 1 c.c. of antivenomous serum. (6) 0·5 c.c. of fresh rat-serum + 1 c.c. of antivenomous serum. To each tube 2 drops of defibrinated horse-blood are added, and the tubes are placed in the stove at a temperature of 35° C. In tubes 1 and 6, which contain fresh rat-serum alone, and fresh serum + antivenomous serum, hæmolysis appears in a few minutes. In tube 4, which received venom alone, hæmolysis is also produced in one hour. It is not produced at all in tubes 2 and 3, which received the neutral mixture of fresh serum and venom, proving that the hæmolytic alexin has been fixed by the venom. The latter, therefore, here plays the part of a true fixator or _amboceptor_. Venom behaves, in short, after the manner of extracts of organs. The fixation of hæmolytic alexin by extracts of organs, the tissues, and animal cells (liver, spleen, spermatozoids, &c., &c.), has already been demonstrated by V. Dungern, P. Müller, Levaditi, and E. Hoke. The same fact is also observed with solutions of peptone. The fixation of alexin is therefore a general property of certain albuminoid molecules.