348 



SCIENCE. 



[N. S. Vol. I. No. 13. 



less susceptible than guinea-pigs, and are 

 more easily made immune. This is most 

 readily accomplished by giving them small 

 and gradually increasing doses with their 

 food. As a result of this ti-eatment the 

 animal resists subcutaneous injections of 

 200 to 300 times the fatal dose for animals 

 not having this artificial immunitJ^ 



Ehrlich gives the following explanation 

 of the remarkable degree of immunity es- 

 tablished in his experiments by the method 

 mentioned : 



' ' All of these phenomena depend, as may easily 

 be 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 later paper (1892) Ehrlich has given 

 an account of subsequent experiments which 

 show that the young of mice which have an 

 acquired immunity for these vegetable tox- 

 albumins may acquire immunity from the 

 ingestion of their mother's milk ; and also 

 that immunity from tetanus may be acquired 

 in a brief time by young mice through their 

 mother's milk. 



A most interesting question presents it- 

 self in connection with the discovery of the 

 antitoxins. Does ■ the animal which is im- 

 mune from the toxic action of any particu- 

 lar toxalbumin also hdve an immunity for 

 other toxic proteids of the same class ? The 

 experimental evidence on record indicates 

 that it does not. In Ehrlich's experiments 

 with ricin and abrin he ascertained that an 

 animal which had been made immune 

 against one of these substances was quite as 

 susceptible to the toxic action of the other 

 as if it did not possess this immunity, i. e., 

 the anti-toxin of ricin does not desti-oy 

 abrin, and vice versa. 



We have also experimental evidence that 

 animals may acquire a certain degree of 

 immunity from the toxic action of the 

 venom of the rattlesnake. This was first 

 demonstrated by Sewall (1887), and has 



been recentlj' confirmed by Calmette (1894) . 

 In his paper detailing the results of his 

 experiments the author last named says : 



' ' Animals may be immunized against the venom of" 

 serpents either by means of repeated injections of 

 doses at first feeble and progressively stronger, or by 

 means of successive injections of venom mixed with 

 certain chemical substances, among which I mention 

 especially chloride of gold and the hypochlorites of 

 lime or soda. 



' 'Tlie serum of animals thus treated is at the same 

 time preventive, antitoxic and therapeutic, exactly 

 as is that of animals immxmized against diphtheria or 

 tetanus. 



" If we inoculate a certain number of rabbits, un- 

 der the skin of the thigh, ^ath the same dose, 1 

 millgr. of cobra venom, for example, and, if we treat 

 all of these animals, with the exception of some for 

 control, by subcutaneous or intraperitoneal injections 

 of the serum of rabbits immunized against four 

 millgrs. of the same venom, all of the control ani- 

 mals not treated will die within three or four hours, 

 while all of the animals will recover which receive 

 5 c. c. of the therapeutic serum within an hour after 

 receiving the venom." 



As a rule the antitoxins have no bacteri- 

 cidal action ; but it has been shown, by 

 the experiments of Gamaleia, Pfeififer and 

 others, that in animals which have an 

 acquired immunity against the spirillum 

 of Asiatic cholera and against spirillum 

 Metchnikovl there is a decided increase in 

 the bactericidal power of the blood-serum, 

 and that immunity probably depends upon 

 this fact. 



Certain important questions present them- 

 selves in connection with the production of 

 antitoxins and germicidal substances in the 

 blood of immune animals, one of which is : 

 Is the production of the antitoxin contin- 

 uous while immunity lasts, or does it occur 

 only during the modified attack which re- 

 sults from inoculation with an attenuated 

 virus, or of filtered cultvires, the antitoxin 

 being subsequently retained in the circula- 

 ting blood? The latter supposition does 

 not appear very plausible, but it must be 

 remembered that these antitoxins do not 

 dialyze — i. e., they do not pass through ani- 



