430 HEPBURN— BIOCHEMIC\L STUDIES 



The solutions, obtained by digestion, were evaporated to dryness, 

 the residue was extracted with absolute alcohol, and the alcohol was 

 removed by evaporation. This residue gave a biuret reaction. Hence 

 tests could not be made ior free tyrosin among the products of the pro- 

 teolysis, for the tyrosin reactions would have been given by the combined 

 tyrosin groups of the albumose and peptone, which were present in the 

 residue from the alcoholic solution. 



Dubois (9) studied the pitcher liquor of the following species of 

 Nepenthes: — coccinea, distillatoria, Hookeriana, hybrida, maculate, phyl- 

 lamphora, Rafflesiana. Before the opening of the operculum, the pitcher 

 liquor of all these species was limpid, sUghtly viscid and slightly acid. 

 In opened pitchers, the Hquor generally was thick, contained whole 

 insects, and, at times, emitted a strong odor of putrefaction. 



When liquor was removed from closed pitchers, which were about to 

 open, and was immediately placed in contact with cubes of coagulated 

 albumen, then incubated at the temperature of the atmosphere, or at a 

 temperature of 35° to 40° C, the albumen was not attacked; the hquor 

 remained limpid at the end of several hours. It was then filtered; the 

 filtrate contained no peptone. The experiment was repeated by trans- 

 ferring the hquor from closed pitchers to Pasteur culture tubes which 

 contained albumen cubes. The results were the same as before; the 

 angles of the cubes remained absolutely intact, and neither micro- 

 organisms nor putrefaction were present at the end of several days. 



Liquor from pitchers, which had been open for but a short time, was 

 still clear. However, it attacked cubes of egg-white, quite rapidly at 

 ordinary temperatures, and very rapidly at the temperature of the incuba- 

 tor. The cubes became swollen, transparent and gelatinous, and lost 

 their angles; the Hquor became viscid, and a distinct odor of putrefaction 

 developed in some of the tubes. The hquor contained numerous micro- 

 organisms of different species and, after filtration, gave some of the 

 reactions of peptone. Many open pitchers contained insects, which were 

 in process of putrefaction and not in process of digestion. 



The manner in which coagulated egg albumen behaved in the presence 

 of the pitcher Hquor — contaminated or not contaminated by micro- 

 organisms — led Dubois to the following conclusions: — 



(1) That the Hquor does not contain any digestive substance (enzyme) 

 comparable to pepsin, and that Nepenthes are not carnivorous plants. 



(2) That the phenomena of disintegration or pseudo-digestion, ob- 

 served by Hooker, were due without any doubt to the activity of micro- 



