112 Immunity 



transfusion, it died of typical tetanus because in tlie brief interval 

 between the toxin injection and the transfusion, the toxin molecules 

 became anchored to the cell. 



The ability of the cells thus to anchor the toxin is supposed by 

 Ehrlich to depend upon the existence of haptophorous combining 

 afiBinities, which he describes as receptors. He views the mode of 

 toxin reception as depending upon a mechanism either identical 

 with or analogous to that by which cellular nutrition is rriaintained, 

 and points out that in the case of methylene-blue and other colored 

 substances, which afford an opportunity to make ocular observations 

 upon the absorption of the pigment by the cells, only certain cells 

 absorb the colors. 



Cell nutrition is therefore probably carried on through the agency 

 of receptors by which appropriate nutrient haptophorous groups are 

 apprehended and utilized. 



The following somewhat lengthy quotation from his "Croonian 

 Lecture upon the Lateral Chain Theory of Immunity," delivered 

 before the Royal Society of London, March 22, 1900, explains the 

 theory in Ehrlich's own words: 



"We now come to the important question of the significance of the toxophile 

 groups in organs. That these are in function especially designed to seize on 

 toxins cannot be for one moment entertained. It would not be reasonable to 

 suppose that there were present in the organism many hundreds of atomic groups 

 destined to unite with toxins, when the latter appeared, but in function really 

 playing no part in the processes of normal life, and only arbitrarily brought into 

 relation with them by the will of the investigator. It would, indeed, be highly 

 superfluous, for example, for all our native animals to possess in their tissues 

 atomic groups deliberately adapted to unite with abrin, ricin, and crotin, sub- 

 stances coming from far-distant tropics." 



"One may, therefore, rightly assume that these toxophile protoplasmic groups 

 in reality serve normal functions in the animal organism, and that they only 

 incidentally and by pure chance possess the capacity to anchor themselves to 

 this or that toxin." 



"The first thought suggested by this assumpticm was that the atom group 

 referred to must be concerned in tissue change; and it may be well here to sketch 

 roughly the laws of cell metabolism. Here we must, in the first place, draw a 

 dear line of distinction between those substances which are able to enter into 

 the composition of the protoplasm, and so are really assimilated, and those 

 which have no such capacity. To the first class belong a portion of the food- 

 stuffs, par excellence; to the second almost all our pharmacological agents, 

 alkaloids, antipyretics, antiseptics, etc." 



"How is it possible to determine whether any given substance will be assimi- 

 lated in the body or not? There can be no doubt that assimilation is in a special 

 sense a synthetic process — that is to say, the molecule of the food-stuff concerned 

 enters into combination with the protoplasm by a process of condensation in- 

 volving loss of a portion of its water. To take the example of sugar, in the union 

 with protoplasm, not sugar itself as such, but a portion of it, comes into play, 

 the sugar losing in the union some of its characteristic reactions. The sugar 

 behaves here as it does,' e.g., in the glucosids, from which it can only be obtained 

 through the agency of actual chemical cleavage. The glucosid shows no traces 

 of sugar when extracted in indifferent solvents. In a quite analogous manner the 

 sugar entering into the composition of albuminous bodies (glycoproteids) cannot 

 be obtained by any rnethod of extraction, at least not until chemical composition 

 has previously taken place. It is, therefore, generally easy by means of extrac- 

 tion experiments to decide whether any given combination in which the cells 

 take part is, or is not, a synthetic one. If alkaloids, aromatic amines, anti- 

 pyretics, or anilin dyes be introduced into the animal body, it is an easy matter, 



