HIGH-MOLECULAR RESIDUAL SUBSTANCES 147 



and hepatic affections (v. Vol. I of this series, p. 550, Chem- 

 istry of the Tissues). The chemical position of the urinary 

 constituent known as "uroferric acid," isolated by Sieg- 

 fried's iron-peptone method, is at present indefinable 76 ; and 

 the same may be said of a substance obtained by P. Hari 77 

 by precipitation by phosphotungstic acid, and the urinary 

 colloids of Salkowski (v. Vol. I of this series, p. 550, Chem- 

 istry of the Tissues) precipitable by salts of the heavy metals 

 and insoluble in alcohol. But it would be a mistake to 

 assume that all nitrogenous colloids of the urine are of the 

 nature of high-molecular protein derivatives. Investiga- 

 tions in the laboratory of F. Hofmeister indicate on the 

 contrary that among the nondialysable urinary constituents 

 (which can be quantitatively estimated by diffusion methods 

 employing very fine fibre capsules), we may meet even such 

 materials as chondroitin-sulphuric acid (Vol. I of this series, 

 p. 281, Chemistry of the Tissues) or nucleinic acid as im- 

 portant compounds ; their quantity may be found increased 

 in renal diseases, in eclampsia and in various febrile states 

 (pneumonia). 78 



It will probably be a long time before the misty atmos- 

 phere at present enveloping these subjects, and in fact cover- 

 ing them as in thick clouds, will be dissipated by the sun. 

 However, even here there is beginning to be a little more 

 light. 



78 O. Thiele, H. Liebermann (Siegfried's Lab., Leipzig), Zeitschr. f. physiol. 

 Chem., 37, 251, 1903; 52, 129, 1907. 



"P. Hari (Budapesth), Zeitschr. f. physiol. Chem., 46, 1, 1905. 



78 K. Sasaki, Hofmeister's Beitr., 9, 386, 1907; M. Savare", ibid., 9, 401; 11, 

 71, 1907; Ch. Pons, ibid., 9, 393, 1907; U. Ebbecke, Biochem. Zeitschr., 12, 

 485, 1908; all from the laboratory of F. Hofmeister, Strassburg. 



