Quite recently an endeavour has been made to determine precisely the degree of toxicity possessed by eel's blood, or, in other words, to standardise the poisonous principle contained in it, so as to afford a guide to those experimenting on the subject; and it has been asserted that one cubic centimetre, or about twenty drops, injected into the veins of a rabbit weighing four pounds, may be regarded as a fatal dose for such an animal. But many difficulties surround such an attempt to exactly define the degree of toxic action possessed by such a substance, for, in the first place, the blood varies in respect to this property in different eels, whilst it also differs widely in character at different stages of the life of the fish. This seasonable variation in toxic character has been noticed in the case of viper venom, which it will be remembered was shown to be far more lethal in action when collected from snakes in the spring of the year than in the winter months. The toxic substance contained in eel serum was originally called by its discoverers, the Mosso brothers, _ittio-tossina_; and they record the fact that the blood of rabbits and frogs, which animals had succumbed to its action, did not coagulate after death, whilst, curiously, in the case of dogs this abnormal phenomenon was not observed. There are various means which may be resorted to for destroying the poisonous principle contained in eel blood, and from a dietetic point of view it is satisfactory to know that heat-exposure for a quarter of an hour to a temperature of from 57·7° to 77·7° Cent. entirely removes it, whilst its virulence is greatly modified by submitting it for a longer period, twenty-four hours, to a much lower temperature, _i.e._ 37° Cent. It also gradually loses its toxic properties eight days after it has been collected, even when carefully shielded from light, a feature which contrasts favourably with viper venom, which can be kept for more than a year and remains as active as when first derived from the snake. We have seen also that its toxic properties invariably succumb to the processes of digestion, so that even if fashion or fad or advertising speculators, backed by scientific names, were to decree that a wealth of nourishment and support was contained in raw eel "juice," and the edict went out that it was a desirable and highly important article of invalid diet, the general public may, according to its wont, innocently accept the edict and in this case suffer no evil consequences.