Experience shows that we may consider as good for therapeutic use serums which, in a dose of 0·05 c.c., completely prevent hæmolysis by 1 decimilligramme of COLUBRINE venom, such as that of Cobra, Krait, &c., and those that in a dose of 0·7 c.c., prevent hæmolysis by 1 milligramme of the venom of _Lachesis_ or _Vipera berus_. By a method calculated upon the foregoing, it is likewise possible to measure the _antihæmorrhagic_ activity of an antivenomous serum, for the parallelism existing between the _antineurotoxic_ and _antihæmolytic_ actions of serums occurs again, as I have been able to establish in conjunction with Noc, between the _antihæmorrhagic_ and _antiproteolytic_ action of the same serums. Now, the _antiproteolytic_ action is easily determined by means of a series of test-tubes containing the same quantity of 20 per cent. gelatinised _bouillon_, rendered imputrescible by the addition of a small quantity of thymol. The gelatine being kept liquid in the incubating stove, a progressively increasing quantity of serum is poured into each tube. The same dose of venom, say 1 milligramme, is then added in each case. The tubes are placed in the stove for six hours at 36° C. They are then withdrawn and immersed in a bath of cold water. Those in which the gelatine solidifies are noted, and thus we establish the dose of antivenomous serum that inhibits the proteolysis of this substance. These different methods of control enable us to verify the activity of antivenomous serums with great exactness, without the necessity of having recourse to experiments upon animals. * * * * * In a very important memoir on the reconstitution of the toxins from a mixture of _toxin_ + _antitoxin_, J. Morgenroth[103] has shown that the venom, after being naturalised by the antivenomous serum, can be dissociated from its combination by means of a method which consists in adding to the latter a small quantity of hydrochloric acid. Previous experiments by Kyes had established:-- (1) That antivenomous serum, the antitoxic action of which is so manifest when it is mixed _in vitro_ with cobra-venom, remains entirely inert when brought into contact with the combination _lecithin_ + _venom_, that is to say, with _cobra-lecithide_. (2) That the addition of lecithin to a neutral combination of _venom_ + _antivenomous_ serum does not set the venom free again, and that under these conditions no _lecithide_ is formed. If, in a neutral mixture of _cobra-hæmolysin_ and _antitoxin_ we could succeed in dissociating the two constituent elements, and in then making the _cobra-hæmolysin_ combine with the _lecithin_, we should have a toxin and antitoxin side by side; for the reasons indicated above, this toxin (_lecithide_) and antitoxin (_antivenomous_ serum) would be no longer capable of combining; but the toxin (_lecithide_), thanks to its hæmolytic properties, could easily be demonstrated.