THE POTATO BACILLI 135 



Fliigge, a plump, actively motile rod, shown in Fig. 43. The colonies on 

 potatoes are dirty white, can be drawn out into threads, and develop equally 

 well in the incubator and at room temperature. This bacillus excretes several 

 enzymes, one being peptonising and producing liquefaction of the medium ; 

 another diastatic ; and a third resembling rennet, whereby the casein of milk is 

 at first precipitated, but is subsequently redissolved by the peptonising enzyme. 

 It forms endospores, the final stage of germination of 

 which is shown at 6 in Fig. 43. 



Bacillus mesentericus fuscus was first described by 

 FLUGGE (I.). The cultures on agar-agar and on 

 potatoes are initially yellow, but as their age in- 

 creases deepen progressively into brown. It also pro- 

 duces a peptonising enzyme, which liquefies nutrient FlG _p tato bacillus, 

 gelatin. The production of spores is in this species a . tw o motile rods ; ft. a newly 



less Copious than in the foregoing and following germinated rod, just having 

 kinds, the spore capsule, and un- 



The vegetative cells of the Bacillus mesentericus ^ d ^rawn f Jom a photo-' 

 ruber, discovered by GLOBIG (II.), are short rods, rather graph by Xetihauss.) 

 more slender in form than those of B. m. vulgatus. 



Like the other two species, the vegetative cells are motile and produce a 

 peptonising enzyme. The colour of the streak cultures on potatoes is at first 

 reddish-yellow, but subsequently becomes rose-red. The tenacity of life ex- 

 hibited by the endospores of this species was minutely examined by Globig. A 

 i per cent, solution of sublimate kills them after ij hours' exposure; but they 

 resist the action of 5 per cent, carbolic acid for more than a fortnight. For 

 their destruction by a current of steam at 100 C. an exposure of 5^ to 6 hours 

 is necessary, and they will bear without injury an immersion of three-quarters 

 of an hour in high-pressure steam at 109-! 13 C. On the other hand, they 

 perish in twenty-five minutes in steam at ii3-ii6 C., in ten minutes at 

 1 22- 123 C., in two minutes at 127 C., and immediately in steam at i3. C : 



The great difficulty of sterilising articles contaminated with traces of soil is 

 due to the great powers of resistance possessed by the spores they contain of the 

 species just described, as also of a large number of their congeners, which are 

 the hardiest of all organisms. The preservation of numerous food-stuffs, milk in 

 particular, is thereby rendered more expensive, as will be sufficiently demon- 

 strated in the two next following chapters. At present, attention will be 

 drawn to a phenomenon which could not well be referred to- there, viz., a 

 disease in bread (due to the potato bacilli), which becomes manifest by the 

 crumb of the loaf gradually changing into a sticky mass, capable of being drawn 

 out into long threads, and having a repulsive sour sweet smell. EMIL LAURENT 

 (II.) was the first to examine this disease closely, and he attributed it to a fission 

 fungus, which presumably also plays a part in the normal fermentation of dough 

 (dealt with in the second volume), and has therefore received the name of 

 Bacillus panificans. This is undoubtedly a species of the group of potato 

 bacilli. A second case of this disease was investigated by KEATSCHMER and NIEMI- 

 LOWIGZ (I.) by the aid of the plate culture method, whereby B. m. vulgatus was 

 recognised as the exciting agent. According to the researches of Aime Girard, 

 reported by BALLAND and MASSON (I.), the temperature prevailing in the 

 interior of loaves of bread during the baking process ranges between 100 and 

 102 C. The duration of exposure to this temperature being insufficient to kill 

 the spores of potato bacilli, those originally present in the flour will still be 

 found alive in the finished loaf. The sites occupied by these organisms, 

 which germinate and reproduce immediately, will then become the headquarters 

 of active masses of microbes, as already described. Batches of bread containing 



