ENDOTRYPTASE. 549 



in preparing a cell-free solution of the enzyme, after demonstrating 

 the presence of a strongly proteolytic enzyme in the expressed 

 juice obtained from yeast by the method of Buclmer and Hahn 

 (see p. 459, vol. ii.), and studying the properties of this enzyme 

 (which he named "yeast endotryptase ") in collaboration with 

 L. GERET (I. and II.). The fission products of autodigestion 

 were afterwards more closely examined by Fr. KUTSCHER (III.), 

 chiefly by the Kossel method. 



The existence of endotryptase can be proved in a most con- 

 venient and striking manner with yeast juice prepared by the 

 method of Buchner and Hahn. A few cubic centimetres of the 

 expressed juice distributed on thymol- or carbol-gelatin (see p. 270, 

 vol. i.), or an ordinary nutrient gelatin with an addition of 

 thymol, in a test-glass, produce a decided liquefaction of the 

 gelatin in twenty-four hours at 22 C., the whole being liquefied 

 in two to three days when 10 c.c. have been taken. The autolysis 

 of the pressed yeast juice is equally convincing and undeniable ; 

 whereas the freshly prepared juice is strongly coagulated by 

 boiling, a decided diminution of the coagulum is observed on boiling 

 the juice after it has been kept, in presence of a little toluol or 

 chloroform, for twenty-four hours at 37 C., a precipitate, how- 

 ever, forming without boiling. The formation of a coagulum is, 

 moreover, almost entirely prevented by storing the juice for six 

 to seven days at 37 C., or ten to fourteen days at room tempera- 

 ture; whilst a deposit of ammo-acids (leucin particularly) is formed. 

 Of course the dried pressed juice, mentioned on p. 463, vol. ii., 

 can be used for the same purpose, after being dissolved in water 

 and treated with an antiseptic. The detection of endotryptase 

 can also be effected with the recently introduced permanent yeast 

 (see p. 481, vol. ii.) on stirring the latter up to a thin pap with 

 water and spreading it on gelatin in presence of toluol. This 

 method, however, never produces such rapid liquefaction as can 

 be obtained by the use of expressed yeast juice. Carmine fibrin 

 (see p. 301, vol. i.) suspended in pressed yeast juice also dissolves 

 in twenty-four hours at 37 C., and stains the liquid dark red ; but 

 the liquefaction of coagulated egg albumen takes longer to accom- 

 plish. WILL (XXXI.) also observed the liquefaction of gelatin 

 in living cultures, with stab cultures of various species of fiaccharo- 

 inycetes (see p. 555, vol. ii.) in wort-gelatin, and kept for eighteen 

 to eighty days at 20 0., or for forty-five to two hundred and forty 

 days at 13 C., the liquefaction usually beginning in the path of the 

 stab. The quantitative determination of the effect produced by 

 endotryptase can also be performed in a most convenient manner 

 with pressed yeast juice, the coagulum produced by boiling the 

 fresh and digested juice being dried and weighed, or else (which is 

 preferable) the increase of nitrogen in the filtrate is ascertained. 

 With this object 10 c.c. of yeast juice are diluted with water, 

 treated with about 5 c.c. of a saturated solution of common salt, 



