J. BRONFENBRENNER 1063 



ble period of incubation and precipitation of the contents with ferric hydroxide, to 

 test the filtrate with ninhydrin. Others have eUminated the ninhydrin test and sub- 

 stituted the colloidal gold test/ or the amino nitrogen determination in its place, ^ To 

 take advantage of the changes in physical properties of the solution resulting from the 

 digestion of protein, measuring the changes in the refractive index, the rate of capil- 

 lary rise, or the conductivity of the solution have been proposed in place of the nin- 

 hydrin test.5 Finally, it has been found that serum is rendered toxic for homologous 

 animals after incubation with a suitable substratum,'' and thus another method of 

 avoiding the use of either thimbles or ninhydrin was made available. ^ All these 

 methods give approximately similar results when compared with the original pro- 

 cedure.* 



VALUE OF THE ABDERHALDEN REACTION AS A DIAGNOSTIC TEST 



In considering the value of these modifications attempting to render the test more 

 reliable, it must be remembered that they all are concerned with demonstration of the 

 products of digestion and can be of service only in so far as they eliminate the errors con- 

 nected with the use of thimbles or of ninhydrin, or both. They cannot be expected to in- 

 crease the specificity of the reaction, since that portion of the procedure on which the 

 specificity of the reaction rests — namely, the preliminary interaction between the 

 serum and the substratum — is identical in all cases. Different samples of a given sub- 

 stratum differ among themselves in their specific value. Whereas one substratum will 

 react with a given serum in any amount above o.i gm., another similar preparation 

 may be found suitable only when used in the amounts of 0.3 gm. or over. On the 

 other hand, different specific sera react differently with a given substratum. Thus 

 for instance, in the case of one specific serum, 0.15 gm. of the substratum may be 

 suflB.cient to elicit the reaction, whereas in another similar case 0.4 gm. or more of the 

 same substratum may be required. It is thus evident that the amount of substratum 

 to be used in the test must be determined in each instance by extensive preliminary 

 inquiry. This difficulty is further increased by a loss of specificity as more substratum 

 is used, since an excess of substratum tends to react also with normal serum. ^ 



The difficulty in establishing the proper dosage of the substratum undoubtedly 



' Matzkiewitsch, J. : ibid., p. 1221. 1914. 



2 Abderhalden, E.: Fermeniforschung, 6, 230. 1922; Abderhalden, E.,and Fodor, A.: Miinchen. 

 med. Wchnschr., 61, 765. 1914; Van Slyke, D., Vinograd-Villchur, M., and Losee, J., 7. Biol. Chem., 

 23, 377- 1915- 



3 Abderhalden, E.: Fermeniforschiing, 6, 119. 1922; Sellheim, H.: Klin. Wchnschr., 4, 247 and 

 299. 1925; Blunck, G.: Miinchen. med. Wchnschr., 69, 1005. 1922. 



4 Bronfenbrenner, J.: Penn. State M. J., 18, 20. Oct., 1914; Proc. Soc. E.vper. Biol, or Med., 11, 

 90. 1914. 



s Smith, G. H., and Cook, M. W.: loc. ciL; Smith, G. H.: lac. cit.; Bronfenbrenner, J., Freeland, 

 J. R., and Schlesinger, M. J.: Am. J . Obst. b" Dis. of Worn, b" Child., 72, 599. 1915; Bronfenbrenner, 

 J., Mitchell, W. J., and Titus, P.: Biochem. Bull., 4, 86. 1914; Kolmer, J. A., and Williams, P. F., 

 Am. J. Obst. 6* Dis. of Wom. &° Child., 71, 899. 1915. 



'Abderhalden, E.: Fermenlforschung, 7, 54. 1923. 



'Flatow, L.: Miinchen. med. Wchnschr., 61, 468, 608, 1168. 1914; Herzfeld, E.: Biochem. Ztschr., 

 64, 103. 1914; Kjaergaard, S.: Ztschr. f. Immunitdtsforsch. u. exper. Therap., Orig., 22, 31. 1914; 

 Plaut, F.: Miinchen. med. Wchnschr., 61, 238. 1914. 



