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 letanus 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 a splinter 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 



