SPORE FORMATION 143 



deep in such a medium. In moulds and yeasts oxygen is essen- 

 tial, and for some spore-bearing bacilli a supply of oxygen is a 

 sine qud non (the exceptions are strict anaerobes like B. tetania 

 B. butyricus, etc.) of sporulation. Prazmowski has pointed out 

 that it is characteristic of these forms that they are non-motile 

 during sporulation. B. tetania B. butyricus, and other strict anae- 

 robes continue to remain motile during sporing. Temperature 

 exerts a marked influence on the process.^ In the. case of 

 B. subtilis, an organism frequently present in milk, spore forma- 

 tion did not occur below 6" C. ; at 18" C. it required two days; at 

 22" C. one day; and at 30° C. only twelve hours.- 



Finally, it may be noted that directly spores find themselves 

 again in a favourable nidus they forthwith germinate into bacilli. 

 The time required for the production of a bacillus from a spore 

 varies with different species. Koch observed the germination of 

 the spore of a B. anthracis to be completed in about sixty minutes. 

 But there is little doubt that this change may occur in less time 

 than that. 



We venture to think that these elementary facts concerning 

 the formation of spores furnish a matter of the first importance to 

 the milk bacteriologist. For from these facts we learn that the 

 lapse of a few hours may bring about very marked changes in the 

 potentiality of a milk as a germ carrier and disease producer. 

 Summarising what we have said we may express the result thus : 

 That a few hours after milking the number of contained organisms 

 is vastly greater than at milking, owing to multiplication in a 

 favourable medium ; that in twenty-four or thirty hours, owing to 

 this increase of bacteria, conditions are beginning to appear in the 

 milk which encourage spore-bearing bacilli to sporulate ; that 

 sporulation may take several hours ; that the spores possess a very 

 high degree of resistance to heat, germicides, or desiccation ; that 

 the spores contain the specific protoplasm of the bacilli 

 producing them ; that the conditions in milk upon which we rely 

 for the limitation or inhibition of bacilli may have no injurious or 

 controlling influence upon spores, which thus pass without check ; 



^ Koch has shown in the case of ^. anthracis that at least 16° C. is necessary 

 for spore formation, and at this temperature limited formation of spores did 

 not occur until after seven days. At 21° C. spores had formed after seventy-two 

 hours, at 25° C. after thirty-five to forty hours, and between 30° C. and 40"" C, 

 in about twenty-four hours ; the best and strongest cultivations were obtained 

 from 20" to 25° C. 



- Y\\i<g^t.— Micro-organisms. Translation by W. Watson Cheyne, 1890, 

 P- 539- 



