450 DESCRIPTION OF SOME SPECIES OF MILK BACTERIA 



to the tube walls, and veil com- 

 posed chiefly of spores. 



Gelatine — Gelatine is slowly 

 liquefied. 



Potato — A thick mucous growth 

 of a dirty yellow colour. 



Milk — No coagulation, but by 

 degrees the liquid takes very slowly 

 the colour and aspect of whey. 

 The diastases are very little active, 

 although manifestly produced. The 

 liquid is alkaline and has a feeble 

 odour ; it contains leucine, tyrosine, 

 and carbonate and valerianate of 

 ammonia. 



The organism in cheese does 

 not develop until a late stage, when 

 its predecessors have prepared for 

 it nutritive matter easily assimi- 

 lated. 



Aerobic. 



Vitality — The organism is killed 

 by a temperature of 90° C. to 95° C. ; 

 the spores resist up to 105° C. to 

 110° C. 



Non-pathogenic. 



TYROTHRIX TENUIS (Duclaux). 



Source and habitat — Milk, and cheese, 

 in the maturation of which it plays 

 an important part. 



Morphology — Bacillus ; 3 m long by -6 

 /It broad. The elements at times 

 take the form of very long filaments, 

 straight or coiled, especially at low 

 temperatures, or when there is 

 scarcity of free oxygen. 



Capsule; motility — No capsule, actively 

 motile in rod form. A gentle 

 undulatory movement when in fila- 

 ments. No movement when the 

 filaments are long or when the ele- 

 ments are formed in long chains. 



Spore formation — Formation of ovoid 

 spores. 



Cultural characters — In bouillon, 

 formation of small whitish flocons 

 at the end of a few hours. 



Milk — Formation of a wrinkled 

 surface pellicle, little coherent ; 

 the milk is coagulated at first under 

 the action of a minute quantity of 

 rennet secreted by the organism, 

 but the coagulum is softer than 

 that produced by ordinary rennet. 

 The casein precipitate is dissolved 

 by degrees by the casease elabor- 

 ated, and the liquid becomes 

 opalescent. Division into elements 

 takes place rapidly, and each of 

 the elements produces an ovoid 

 spore ; the surface veil is soon 

 almost entirely invaded with these 

 spores. The organism is strictly 

 aerobic. 



Vitality — Its resistance to heat 

 is remarkable. The spore forming 

 elements, in a neutral liquid only 

 perish at from 90"* C. to 95° C. ; in 

 a medium feebly alkaline they can 

 spore at 100° C. The spores will 

 bear a temperature of 1 1 5° C. The 

 optimum temperature for cultures 

 is from 20° C. to 25° C. 



Winckler has obtained from cul- 

 tures of Duclaux several varieties of 

 this species. One of which, lique- 

 fying gelatine, is a strong peptoniser 

 of casein ; another, which does 

 not liquefy lactose gelatine, sets up 

 a powerful lactic fermentation ; 

 another gives rise in liquid media 

 to a greenish fluorescence and to 

 formation of a reddish pigment 

 upon potato. 



TYROTHRIX TURGIDUS 



(Duclaux). 



Source and habitat— Cheese. 



Morphology — Bacillus with square 

 ends sharply defined; i m broad 2 to 

 3 p. long. Rarely isolated, more 

 often united in chains of some 

 length. 



Capsule; motility — No capsule ; non- 

 motile. 



Spore formation — Forms spores. 



