466 Prof. D. A. Welsh and Dr. H. G. Chapman. [Apr. 30, 



reversed. Incomplete inhibition was manifested by delay in appearance or 

 by diminution in amount of the precipitate, or by both phenomena. 



When complete inhibition was established, it did not cease with lapse of 

 time, nor was it overcome by any excess of homologous protein, but it could 

 be overcome (that is a precipitate would appear) on a suitable addition of 

 unheated antiserum, or on a smaller addition of unheated antiserum together 

 with homologous protein. 



When, as occasionally happened, 01 c.c. heated antiserum was inadequate 

 to prevent precipitation in a mixture of 0*001 c.c. or 0*005 c.c. homologous 

 protein and 0*1 c.c. unheated antiserum simultaneously added, it was 

 invariably also inadequate when allowed to stand in contact with the unheated 

 antiserum for 24 hours before homologous protein was added, but it was 

 frequently adequate to prevent precipitation when allowed to remain in 

 contact with the homologous protein 24 hours before the unheated antiserum 

 was added. In view of the fact that no excess of homologous protein could 

 overcome any inhibition, it is futile to conclude from such evidence that the 

 heated antiserum antagonises either the homologous protein or the unheated 

 antiserum more than the other. As a matter of fact, its influence is probably 

 exerted not so much on either of the interacting substances as on the product 

 of their interaction (v. infra). 



Analogous results have been obtained by other observers, notably by 

 Miiller,* in respect of lactosera, and by Eisenberg.f 



Relation between Inaetivation and Inhibition. 



On the hypothesis that precipitins constitute, on Ehrlich's scheme, 

 receptors of the second order, equipped with a relatively unstable ergophorous 

 and a relatively stable haptophorous affinity, inaetivation is produced by 

 destruction of the former, while inhibition is due to retention of the latter 

 alone. Any factor that would abolish the ergophorous affinity would, ipso 

 facto, render the precipitin inactive and inhibitory, so long as the haptophorous 

 affinity was not thereby damaged. Precipitin would thus become transformed 

 into precipitoid. In other words, inaetivation and inhibition would be merely 

 different aspects of the same phenomenon, and this is the accepted relation- 

 ship between them (Eisenberg, Miiller, and others). 



We have evidence, however, that inaetivation and inhibition are separable 

 phenomena, that inaetivation does not, in the above circumstances, necessarily 

 imply inhibition, so that the relation between them does not admit of so 



* Miiller, ' Archiv f. Hygien.,' vol. 44, p. 126, 1902. 



t Eisenberg, ' Centralb. f. Bakt. : (Originale), vol. 31, p. 773, 1902. 



