772 THERMOLABILITY OF COMPLEMENT 



permanently inactivate complement. The destructive or inhibitory- 

 effect of slight degrees of acidity or alkalinity has been noted by a 

 number of later workers. Liefmann and Cohn,^ and Guggenlieimer^" 

 found that the isolated mid-piece is more affected by the chemical 

 reaction than is the end-piece; both fractions are more affected 

 by acid than by alkali. Michaehs and Skwirsky" and Leschly^ 

 have worked with definite H ion concentrations, but their results do 

 not relate to the present problem. Brooks^^ ^^g recently defined 

 the limits of pH value of the acidity beyond which complement 

 is permanently inactivated. 



The salt concentration of the solution has been found to affect 

 complement in a way which appears to be quite different from that 

 in which the two fractions of complement are separated by dilution 

 with distilled water and dialysis, as in the original method of Ferrata.^ 

 Sachs and Teruuchi" found that when fresh serum is diluted 1 to 

 10 with distilled water a permanent inactivation occurs, and takes 

 place more rapidly at 37°C. than at lower temperatures. 



In the present work the degree of complementary activity retained 

 by fresh guinea pig serum after being heated to various temperatures 

 in solution in distilled water or in sahne solution, at definite H ion 

 concentrations, has been determined by a modification of the method 

 of Brooks." This consisted in measuring in a colorimeter to provide 

 a standard for comparison the percentage of hemolysis given by the 

 following amounts: 1, 0.8, 0.6, 0.4, 0.3, 0.2, 0.1, and 0.05 cc. of a 

 dilution of each specimen of serum in saline solution. This dilu- 

 tion was first made 1 to 20, and then slightly increased to cor- 

 respond exactly to the final dilution of the samples which were 

 heated under varying conditions of temperature and reaction. The 

 degrees of hemolysis thus observed were plotted as ordinates 

 against the amounts of complement dilution as abscissae. From 

 the curve so obtained the relative efficiency or activity of each 



^Leifmann H., and Cohn, M., Z. Immunitdtsforsch. Orig., 1910, vi, 562. 

 ^^ Guggenheimer, H., Z. Immunitdtsforsch. Orig., 1911, xi, 393. 

 ^^ Michaelis, L. and Skwirsky, P., Z. Immunitdtsforsch. Orig., 1910, vi, 357, 629 

 12 Brooks S. C. ,/. Gen. Physiol, 1919-20, 185. 

 " Sachs, H., and Teruuchi, Y., Berl Klin. Woch., 1907 xliv, 467. 

 "Brooks, S. C, J Med. Res., \9\9-20,x\\, 2,99. 



