SUSCEPTIBILITY AND IMMUNITY. 263 
subcutaneous injections of two hundred to four hundred times the 
fatal dose for animals not having this artificial immunity. The fatal 
dose of abrin is about double that of ricin. When injected into mice 
in the proportion of one cubic centimetre to twenty grammes of body 
weight a solution of one part in one hundred thousand of water 
proved to be a fatal dose. The local effects are also less pronounced 
when solutions of abrin are used ; they consist principally in an ex- 
tensive induration of the tissues around the point of injection and a 
subsequent falling off of the hair over this indurated area. When 
introduced into the conjunctival sac, however, abrin produces a 
local inflammation in smaller amounts than ricin, a solution of 1:800 
being sufficient to cause a decided but temporary conjunctivitis. 
Solutions of 1:50 or 1:100 of either of these toxalbumins, introduced 
into the eye of a mouse, give rise to a panophthalmitis which com- 
monly results in destruction of the eye. But in mice which have 
been rendered immune by feeding them for several weeks with food 
containing one of these toxalbumins, no reaction follows the intro- 
duction into the eye of the strongest possible solution, or of a paste 
made by adding abrin to a little ten-per-cent salt solution. Ehrlich 
gives the following explanation of the remarkable degree of im- 
munity established in his experiments by the method mentioned: 
** All of these phenomena depend, as may be easily shown, upon 
the fact that the blood contains a body—antiabrin—which completely 
neutralizes the action of the abrin, probably by destroying this body.” 
In a more recent paper Ehrlich has given an account of subse- 
quent experiments which show that the young of mice which have 
an acquired immunity for these vegetable toxalbumins may acquire 
immunity from the ingestion of the mother’s milk; and also that 
immunity against tetanus may be acquired in a very brief time by 
young mice through their mother’s milk. In his tetanus experi- 
ments Ehrlich used blood serum from an immune horse to give im- 
munity to the mother mouse when her young were already seven- 
teen days old. Of this blood serum two cubic centimetres were 
injected at a time on two successive days. The day after the first 
injection one of the sucklings received a tetanus inoculation by 
means of asplinter of wood to which spores were attached. The 
animal remained in good health, while a much larger control mouse 
inoculated in the same way died of tetanus at the end of twenty-six 
hours. Other sucklings, inoculated at the end of forty-eight and of 
seventy-two hours after the mother had received the injection of 
blood serum, likewise remained in good health, while other control 
mice died. 
The possibility of conferring immunity by means of the milk of 
an immune animal is further shown by the experiments of Brieger 
