November ai, 1902.] 



SCIENCE. 



80tJ 



adapted primarily to physiological iises.* 

 To the foregoing inquiry Ehrlich answers 

 that the mechanism concei-ned is one 

 physiologically employed for the assimila- 

 tion by the cells of food. The receptors 

 are in the cells, not for the purpose of link- 

 ing poisons to the cells but to seize certain 

 food stuffs, particularly the proteids, and 

 the toxins and bacterial and other foreign 

 cellular substances, if capable of inducing 

 the immunizing reaction, chance to have 

 the requisite combining affinities for the 

 food receptors. It is interesting that 

 Metchnikoff also, though from a different 

 point of view, refers the mechanism of im- 

 munity to the physiological function of 

 assimilation of food by the cells. 



Inasmuch as, according to Ehrlich 's 

 hypothesis, the specific antagonistic sub- 

 stances resulting from the injection of 

 toxins and of foreign cells or derivatives 

 of cells exist preformed in cells of the nor- 

 mal body, there would appear to be no 

 reason why any one of them might not 

 occasionally be present normally free in 

 the blood or other fluids. In fact, many 

 of them— such as diphtheria and tetanus 

 antitoxins, various antienzymes, bacteri- 

 cidal, hasmolytic and other cellular toxins, 

 agglutinins and a number of other bodies 

 of this class, as well as their antibodies- 

 have been found repeatedly, though of 

 course in the case of many inconstantly 

 and with marked differences between indi- 

 viduals and species, in the blood of healthy 

 human beings or animals when their 

 presence could not reasonably be attrib- 

 uted to a previous specific immunization. 

 Of these normal antibodies the only one 

 which is increased in amount by the pro- 

 cess of immunization is that specifically 

 related to the material used to bring about 

 the reaction. As already stated, it is the 



* W. H. Welch, ' Adaptation in Pathological 

 Processes,' Trans. Congress American Physicia/ns 

 and Surgeons, 1897, Vol. IV. 



intermediary body,* not the complement, 

 which is generated in immunization against 

 bacteria and other cells. 



The foregoing statements, though of 

 necessity condensed and incomplete, about 

 the general characters of the specific anti- 

 bodies will, I trust, help to a better under- 

 standing of what is to follow concerning 

 the bearing of some of these discoveries on 

 medical science and practice. I realize 

 the difficulties which you must already 

 have experienced, if unfamiliar with these 

 new lines of research, in following a brief 

 presentation of a subject in which not only 

 are the facts so complex, and the ideas so 

 novel, but the terminology so strange and 

 burdened with such a multitude of con- 

 fusing synonyms. Wlule deploring the 

 multiplication of unnecessary new terms, 

 I should like to quote in this connection a 

 wise remark of Huxley :f 



' ' If we find that the ascertainment of the 

 order of nature is facilitated by using one 

 terminology, or one set of symbols, rather 

 than another, it is our clear duty to use 

 the former; and no harm can accrue so 

 long as we bear in mind that we are deal- 

 ing merely with terms and symbols." 



The most remarkable and characteristic 

 attribute of these antibodies is the speci- 

 ficity of their relation to the substances 

 which have led to their formation. Of 

 some of them, such as diphtheria or tetanus 

 antitoxin, this specificity is nearly absolute ; 

 of other, such as the precipitins, it is only 

 relative. This property is the basis of new 

 and most valuable methods for the identi- 

 fication of species and the determination of 

 genetic relations— species not only of living 



* I use in this lecture the name ' intermediary 

 body ' in preference to the more technical term 

 ' amboceptor,' although Ehrlich applies the Ger- 

 man equivalent — Zicisclienkdrper — only to normal 

 as distinguished from immune amboceptors. 



t Huxley, ' On the Physical Basis of Life,' ' Col- 

 lected Essays,' Vol. I., p. 164, New York, 1893. 



