86 The Preciiyitins: Methods 



After dilution, the solutions were neutralized, and then tested quanti- 

 tatively. Control antisera were also used in all cases, but gave no 

 reactions. 



The effects of the presence of unneutralized acids and alkalis have 

 been given previously (p. 82). 



The preceding table (p. 85) shows that, except in very small quan- 

 tities, the prolonged action of inorganic acids completely destroys the 

 precipitable substance, but that organic acids do not exert so dele- 

 terious an influence. Strong alkalis act in the same way as inorganic 

 acids." 



6. Precautions with regard to Quantitative Tests by my Method. 



It is obvious that if either antiserum or the serum to be tested 

 undergo concentration by evaporation the figures obtained will be 

 fallacious. The possibility of serum becoming concentrated in cor pore, 

 in consequence of disease, has been referred to on page 80. It is 

 naturally essential that there shall be no matter in suspension, or 

 bacterial multiplication occurring in either the test serum or blood 

 dilution. 



7. Bacterial Multiplication. 



I have referred to an objection to weak and slowly-acting antisera 

 being the opportunity which is given to bacteria to develope, when 

 tubes are left standing as long as 24 hours, especially when they are 

 placed at higher temperatures as has been done in experiments of 

 some investigators. In my experiments I have on several occasions 

 had my later readings vitiated by bacterial development, especially 

 during summer, the readings being made after 24 hours and the tubes 

 kept at room temperature. The object of thus prolonging the experi- 

 ment was to note the deposits formed in the solutions overnight. 

 I sought to guard against this by noting the deposits earlier or later, 

 depending upon the temperature of the room in which the experiments 

 were made; in summer the deposits were noted after 12 — 16 hours, in 

 winter after 24 or more hours. 



Where bacteria develope, provided that the readings are made 

 sufficiently early, there will be little chance of confusing the clouding 

 produced by microorganisms, with what I wished to note, namely the 

 deposit at the bottom of the tube. A little experience renders it easy 

 to as a rule recognize early bacterial cloudings, for they generally arise 

 from the lower strata of the fluid, gradually float upward, the bacteria 



