Degrees of Reaction 143 



added to these bloods in solutions of equal strengths, the anti-human 

 serum in its highest dilution, only acted upon human blood dilutions. 



The dilution-method has not been adopted in the study of blood- 

 relationslilps, and these are the only figures obtained by the method 

 which I have come across. The importance of making a series of 

 dilutions of a suspected blood in medico-legal work, is made parti- 

 cularly clear by the figures of Linossier and Lemoine, given above. 



It is evident that one observer will record a reaction and another 

 not, when using the dilution-method without reference to time, and 

 undoubtedly faint cloudings will be completely overlooked if the fluids 

 are examined in an unsuitable light (see description of my apparatus, 

 p. 70 and Fig. 4). There is consequently a considerable subjective element 

 in the tests conducted by the dilution-method, which is absent from my 

 method of actual measurement. 



Eisenberg (5, v. 1902, p. 290) considers a "unit of precipi table 

 substance " to be that minimal quantity, which, when contained in 

 a given volume of fluid, suffices to produce a specific reaction. Thus, 

 when a given albuminous solution (dilution 1 : 1000) yields a precipitum, 

 then 1 c.c. thereof contains 1000 units of precipitable substance. The 

 "unit of precipitin," is that minimal quantity which just suffices to 

 produce a reaction in any albuminous solution. For example when an 

 antiserum still produces a precipitation in a 1 : 100 albumin dilution, he 

 would say it contained 100 precipitin units per c.c. It seems to me 

 until we know more about the possible existence of normal anti- 

 precipitins in sera, it is somewhat premature to attempt an exact 

 standardization either of the precipitin or precipitable substance. 

 Nevertheless the method suggested may have its use, unless my method 

 of volumetric measurement is preferred. I have standardized my 

 antisera, simply by stating the amount of precipitum produced as may 

 be seen by my table of measurements quoted on p. 145. This is again 

 stated in most cases for the antisera with which my tests were made in 

 the following tables. It will be seen I express the " strength " of my 

 antisera simply in terms of precipitum amounts. 



To study the quantitative relations of the interacting bodies, 

 Eisenberg (loc. cit. p. 291) adds a constant amount of one substance to 

 a variable amount of the other, and, after reaction has taken place, 

 he determines the absolute as well as the relative absorption of precipitin. 

 As in agglutination experiments, the amount of absolute absorption 

 is defined in terms of the difference between the number of precipitin- 

 units present in the fluid per unit of volume, before and after reaction 



