DUCLAUX' STUDIES ON CANTAL CHEESE. 319 



"by E. DUCLAUX (VII. and XIII.) in his studies on Cantal cheese, 

 from which he isolated ten species of Scliizomycetes, and classified 

 these under the common generic name of Tyrothrix, belonging to 

 the large sub-group of the so-called hay and potato bacilli. Out 

 of these ten species, one, T. virgula, being unable to grow in milk, 

 will be omitted from further consideration. Each of the remaining 

 nine produces two classes of enzymes, one resembling lab and 

 coagulating milk, whilst the other, casease ( 147), dissolves and 

 splits up the albumin thus precipitated. This proteolytic enzyme 

 can be thrown down from the bacterial cultures by means of 

 alcohol. A particularly abundant yield is obtained from Tyrothrix 

 tenuis, an actively motile, sporogenic rod about 0.6 /x broad and 

 3 ju, long, and often growing in the form of filaments ; hence the 

 name Tyrothrix (= cheese-thread, cheese-hair). This species is 

 aerobic, as are also T. filiformis, T. distortus, T. gemctdatus, T. 

 turgidus, and T. scaber ; whilst T. uroeephalum, T. daviformis, and 

 T. catenula are, on the other hand, anaerobic. Cultures of Tyro- 

 thrix tenuis obtained from Duclaux' laboratory were investigated 

 in 1895 by W. WINKLER (I.), who formed the opinion that this 

 species can be modified, by cultivation, into three varieties or 

 races. This was, however, contradicted by J. WITTLIN (I.) in 

 1896. 



The metabolic products, e.g. leucine, tyrosine, and the am- 

 monia salts of acetic, valeric, and carbonic acids yielded by the 

 Tyrothrix species are the identical substances we have seen to be 

 produced in the ripening of cheese. This concordance necessarily 

 strengthens Cohn's hypothesis, that the ripening of cheese is 

 effected by the vital activity of micro-organisms. On this point, 

 however, Duclaux was unable to afford any certain proof. Later 

 workers attempted to arrive by various ways at a solution of this 

 highly important matter, and mostly by endeavouring to ascer- 

 tain whether the ripening of cheese could be accomplished in the 

 absence of any fermentative organisms. F. SCHAFFER and ST. 

 BONDZYNSKI (I.) showed that curd prepared from boiled milk does 

 not ripen ; and, according to FREUDENREICH (III. ), the same applies 

 equally to Pasteurised milk. Moreover, L. ADAMETZ (VI.) found 

 that neither does ripening occur when bactericidal substances, such 

 as thymol or creoline, are added to the fresh curd ; and the same 

 result was attained by L. PAMMEL (I.) by the use of hydrogen 

 peroxide. 



177. Changes in the Bacterial Flora of Ripening 



Cheese. 



L. Adametz also attempted to ascertain the active cause of the 

 ripening process in a new way, namely, by tracing the quantitative 

 and qualitative alterations occurring in the bacterial content of the 

 ripening curd. These researches made on a Sornthal (Switzer- 



