370 CHEMICAL ANALYSIS OF ASPERGILLACE^l. 



yet available as to the nature of the proteolytic enzyme or 

 enzymes. That of Penic. glaucum w&s extracted by A. HANSEN (I.) 

 in 1889 from the vegetations by means of glycerin. The solution 

 converted neutral gelatin into glutopeptone more rapidly than 

 acid gelatin, whether sugar were present or not. Isolation by 

 precipitation with alcohol was found to be impracticable, the 

 resulting precipitate being inoperative. Possibly the quantity 

 obtained was too minute, since the experiments showed that the 

 substance is actually excreted by the hyphse into the substratum, 

 and acts at considerable distances, as well as through an artificial 

 collodion film. 



STOLL (I.) carried out a series of comparative experiments on 

 the proteolytic power of Penicillium species, the influence of the 

 reaction of the medium being also observed, normal, acid (acidified 

 with normal sulphuric acid), and alkaline (with normal caustic 

 soda) gelatin and sugar gelatin (containing 2 per cent, of dex- 

 trose) being employed at a uniform temperature. Penic. brevicaule 

 liquefied alkaline gelatin more quickly than the acid sample (4-6 

 days), but did not liquefy sugar gelatin, though this latter was 

 very gradually liquefied by Penic. glaucum under the ordinary 

 experimental conditions. Increased additions of alkali or acid 

 seemed to favour the action in this latter case, whereas further 

 additions of sugar had a contrary effect. Penic. olivaceum lique- 

 fied the same acid and alkaline gelatin only after nearly four 

 weeks, whilst sugar gelatin remained unaltered at the end of a 

 fortnight. Penic. italicum also had no effect on sugar gelatin, 

 though it acted on acid or alkaline gelatin after about a fortnight, 

 the same behaviour being observed with Penic. rubrum and Penic. 

 purpurogenum. Hence, with the exception of " Penic. glaucum" 

 the addition of sugar prevented the liquefaction of gelatin (see 

 also p. 63, vol. ii.). The previously mentioned experiments, and 

 the observations of Malfitano, show that these results must not be 

 taken, unconditionally, as generally applicable, other circum- 

 stances, such as the concentration of the gelatin, the presence of 

 other nutrient substances, &c., having to be considered, since 

 Penic. brevicaule, for example, is known to have a decided liquefy- 

 ing influence on 10 per cent, wort gelatin (i.e., gelatin and sugar). 

 Further particulars on the behaviour of four species of Aspergillus 

 toward gelatin will be found in a recent work by TIRABOSCHI (II.). 



The fact that an extract from Asp. niger soon dissolves fibrin 

 and coagulated egg albumen, and also liquefies gelatin was 

 already reported by Bourquelot. MALFITANO (I.), who was the 

 first to investigate this point more fully, found that the method 

 of nutrition was immaterial as regards the formation of the 

 proteolytic enzyme (" protease "), this apparently diosmotising 

 only after the death of the cell. It can be recovered by drying 

 and grinding young and still living vegetative growths, and then 

 extracting them with chloroform water, and using alcohol as a 



