This is not, however, the way in which the phenomenon should be understood, for it is impossible to admit the identification of heated serum or lecithin with the complementary substances or alexins, seeing that the essential characteristic of the latter is that they are intolerant of heat and become entirely inactive on being raised to a temperature of 58° C., or even by simply being kept for a few days exposed to the air and light. We must therefore suppose, with P. Kyes and H. Sachs, that the red corpuscles themselves contain substances capable of playing the part of complements (_endo-complements_), and that it is with these that the venom combines when quickened by the presence of lecithin or heated serum, the latter only acting because it contains free lecithin. All substances that contain lecithin, such as bile, hot milk, or cephalin, are capable of exerting the same quickening action, but do not themselves possess any inherent hæmolytic power. _Cholesterin_, on the contrary, represents a kind of antidote to lecithin, as also to normal serums. It prevents hæmolysis of the red corpuscles in a mixture of washed corpuscles and venom, yet it does not in any way modify the properties of true alexins or complements. Moreover, no correlation exists between _lecithides_ and the _neurotoxin_ in venoms. The combination lecithin + venom possesses _hæmolytic_ action, but is in no way _neurotoxic_. Conversely, venom can be freed from its groups of molecules combinable with lecithin, and remain _neurotoxic_. _Lecithide_ is insoluble in ether and acetone, but soluble in chloroform, alcohol, toluene, and water. Its properties are therefore entirely distinct from those of its two components. It precipitates slowly from its aqueous solutions, without losing its hæmolytic power; it does not show _biuret_-reaction; it dissolves with equal readiness the red corpuscles of all species of animals, and its effects, like those of venom, are impeded by cholesterin. Kyes has succeeded in obtaining lecithides with all the hæmolytic venoms that he was able to study: thus he has prepared lecithides from _Lachesis lanceolatus_, _Naja haje_, _Bungarus_, _Lachesis flavoviridis_, and _Crotalus_. It is therefore probable that the _lecithinophile_ group exists in all venoms, even when these differ as regards their other properties.