March 29, 1895.] 



SCIENCE. 



347 



against which immunity exists, or of de- 

 stroying the germ itself. 



Tlie sulistances which destroy the toxic 

 products of pathogenic bacteria are called 

 antitoxins. As pointed out by Buchner in a 

 recent paper, the antitoxins differ essentially 

 from the so-called alexins, to which natural 

 immunity is ascribed. The alexins are char- 

 acterized by their germicidal and globulici- 

 dal action — they destroy both the red cor- 

 puscles and the leucocytes of animals belong- 

 ing to a different species fi-om that from 

 which they have been obtained, and by 

 their coagulability and instabilitj' — de- 

 stroyed by sunlight and by a temperature 

 of 50° to 55° C. On the other hand, the 

 antitoxins best known (diphtheria and te- 

 tanus) have no germicidal or globulicidal 

 action ; they resist the action of sunlight 

 and require a temperature of 70° to 80° C. 

 for their destruction. 



Our knowledge of the antitoxins dates 

 ft'om the experiments made in the Hygienic 

 Institute of Tokio, by Ogata and Jasuhara. 

 in 1890. These bacteriologists discovered 

 the important fact that the blood of an 

 animal immune against anthrax contains 

 some substance which neutralizes the toxic 

 products of the anthrax bacillus. 



In the same year (1890) Behring and 

 Kita.sato discovered that the blood of an 

 animal wliich has an acquired immunity 

 against tetanus or diphtheria, when added 

 to a virulent culture of one or the other of 

 tbe.se bacilli, neutralizes the pathogenic 

 power of such cultures, as shown by inocu- 

 lation into susceptible animals. And also 

 that cultures from which the bacilli have 

 been removed by filtration, and which kill 

 susceptible animals in very small amounts, 

 have their toxic potency destroyed by adding 

 to them the blood of an immune animal, 

 which is thus directly proved to contain an 

 antitoxin which comparative experiments 

 show not to be present in the blood of non- 

 immune animals. 



During the past two or three years nu- 

 merous additional experiments have been 

 reported which confirm the results already 

 referred to, and show that immunity may 

 be produced in a similar manner against the 

 toxic products of various other pathogenic 

 bacteria — the typlioid bacillus, the ' colon 

 bacillus,' streptococcus pyogenes, staphylo- 

 coccus pyogenes aureus and albus, etc. 



The Italian investigators, Tizzoni and 

 Centanni, in 1892. published a preliminary 

 communication in which they gave the re- 

 sults of experiments which appear to show 

 that in guinea-pigs treated with tuberculin . 

 by Koch's method, a substance is devel- 

 oped which neutralizes the pathogenic po- 

 tency of the tubercle bacillus. Professor 

 Tizzoni and his associate. Dr. Schwarz, have 

 also (1892) obtained evidence that there is 

 an antitoxin of rabies. Blood-serum taken 

 from a rabbit having an artificial immunity 

 against this disease was found to neutralize, 

 in vitro, the vii'ulenee of the spinal marrow of 

 a rabid animal after a contact of five hours. 



Professor Ehrlich, of Berlin, in 1891, 

 published the results of some researches 

 which have an important bearing upon the 

 explanation of accpiii'ed immunity, and 

 which show that susceptible animals may 

 be made immune against the action of cer- 

 tain toxic proteids of vegetable origin, 

 other than those produced by bacteria ; 

 also that this inmiunity depends upon the 

 presence of an antitoxin in the blood-serum 

 of the immune animals. 



The experiments of Ehrlich were made 

 with two verj' potent toxalbumins — one 

 ricin, from the castor-oil bean ; the other, 

 abrin, from the jequirity bean. The toxic 

 potency of ricin is somewhat gi-eater than 

 that of abrin, and it is estimated by Ehr- 

 lich that 1 gm. of this substance would suf- 

 fice to kill one and a half million of guinea- 

 pigs. When injected beneath the skin in 

 dilute solution it produces intense local in- 

 flammation, resulting in necrosis. Mice are 



