PROTEOLYTIC ENZYMES 231 



called Thymol-gelatin is prepared in the following manner: Water saturated 

 with thymol is qualified with 510 per cent, of purest gelatin, and after being 

 warmed on the water-bath is poured into test-tubes (10 c.c. in each). The 

 tubes are kept in a vertical position, and are ready for immediate use as soon as 

 the contents have set. The thymol present therein will prevent any develop- 

 ment of bacteria. A large stock of these tubes can be prepared, and the contents 

 preserved from desiccation by placing the (open) tubes, mouth downwards, in 

 a covered glass vessel containing a little distilled water. The liquid to be 

 examined is filtered to remove any solid particles. A few c.c. are then placed 

 in one of the thymol-gelatin tubes, and a little thymol is added to prevent the 

 development of any bacteria already present in the sample. The tube being 

 then left to stand at room temperature, the presence of any proteolytic enzyme 

 in the sample will be revealed in a few days by the liquefaction of an appreciable 

 stratum of the gelatin. To enable this change to be reliably ascertained a mark 

 is made on the tube at the time of filling, to denote the level of the gelatin. 

 The risk of the gelatin becoming dissolved by any large percentage of acid or 

 alkali present should be obviated by neutralising the sample before commencing 

 the experiment. Liquids containing substances such as tannin, glycerin, &c., 

 capable of preventing or retarding the solution of the gelatin, are unsuitable 

 for use. This simple method may also be employed as an approximate 

 quantitative test for determining the relative strength of two solutions of a 

 proteolytic enzyme, since the amount of gelatin dissolved per unit of time under 

 identical conditions may be regarded as a measure of the concentration or 

 potency of the samples. If tubes of equal diameter are used, then this relation 

 is simply expressed by the height (thickness) of the two liquefied strata. Fermi 

 claims that his method is more reliable than those proposed (for the same 

 purpose) by Griinhagen, Griitzner, Briicke, and Schiitz, and which consist 

 chiefly in determining the amount of Jibrin dissolved by the sample under 

 certain definite conditions. As we have already mentioned that this latter 

 substance is attacked with greater difficulty than gelatin, it will be at once 

 evident that Fermi's method is the more delicate. 



With regard to casease, i.e. the enzyme decomposing the casein of milk into 

 soluble products, the chief particulars have already been given in 147. Many 

 bacterial species are, however, capable of dissolving this albuminoid without any 

 trace of casease being found in the cultures. One of these is the Bacterium 

 peptofaciens, isolated from milk by AL. BERNSTEIN (I.), which is particularly 

 active in converting casein into peptone and albumoses, a little (0.2 per cent.) 

 lactic acid being also formed. If, now, the milk be boiled after the bacterium 

 has been in action for a short time, the unconverted casein will be thrown down, 

 and, when filtered off, leaves behind a liquid which is rich in readily digestible 

 peptones, and has been named " galactone " by its inventor. The milk-sugar 

 present in this liquid may be fermented by the addition of suitable yeasts, and 

 then yields " galactone wine." 



The bacteriological researches of the past few years have resulted in an 

 important modification of the opinions held regarding the so-called carnivorous 

 plants. According to earlier statements, the glands of the parts of the plant 

 acting as a snare secreted a dissolving albumen enzyme, which digested the 

 captured prey, i.e. converted its albuminoids into assimilable peptones, &c. 

 Hoppe-Seyler in 1876 threw doubts on the presence of this enzyme in Drosera 

 rotundifolia, and in 1889 N. TISCHUTKIN (I.) ascribed the phenomenon to 

 bacterial activity. 



This observer ascertained that the juice collecting on the surface of the 

 leaves of Pinguicula is rendered inactive by painting the leaves over with 

 bactericidal media. The same conclusion was arrived at by R. DUBOIS (II.) in 



