1878.] the Life-History of a Minute Septic Organism. 343 



in a fluid is " perfectly easy," is a serious mistake. He thinks that we 

 have nothing to do but to " put one or two drops of the fluid into 

 a small tube .... hermetically seal it, and then heat it for ten 

 minutes or more to different degrees before subjecting the fluid to a 

 prolonged microscopical examination." 



Certainly this is a " perfectly easy " method ; but it must fail entirely 

 to secure the end in view. "What certainty could we have that the 

 spore — in the'only useful condition for experiment — the freshly emitted 

 state — would be in the " one or two drops ? " Spores in various stages 

 of development undoubtedly would be there. But I make no affirmation 

 about these. There can scarcely be a doubt that germs partly developed 

 must succumb at a far lower temperature. Then it follows that 

 the certainty and the uniformity of results must depend upon the 

 certainty we possess, as to whether the spores were in the fluid before 

 heating or not. And when we remember that the phenomenon of 

 fission may, in some monads, go on in a drop of fluid under examina- 

 tion as the sole method of increase for a week or more ; and that, in all 

 cases the production of the spore is extremely rare in relation to the 

 other morphological changes, the force of this will be even more 

 manifest. 



But in thinking out the best method of determining as delicately 

 as possible the thermal death-point of the adult, it occurred to me, 

 that having demonstrated the existence of the spore, and having watched 

 the development after it had endured given heat-conditions, that it 

 would be possible to adopt means for comparing the differences that 

 might exist between the destructive influence of a given temperature 

 endured in " dry " and moist conditions respectively. 



My plan was to arrange the form of the vessel in which the fluid was 

 heated, so that without subsequent transference or exposure the fluid 

 could be directly examined by the lens. This end was secured by 

 means of extremely delicate glass blowing. The apparatus is pre- 

 sented in diagram at figs. 26 and 27.* In fig. 26 A is a hollow bulb, 

 intended as a reservoir for an infusion containing any required 

 organism or organisms. The infusion is put in through the funnel 

 and tube B. The bulb A opens into a tube D on the opposite side, 



on the 77th page of the paper, and will be referred to in a paper which I hope 

 shortly to send to the Eojal Microscopical Society. 



* A large number of these pieces of apparatus have been made for me by a friend, 

 an amateur. But for exquisitely finished and accurate work I have been enabled to 

 obtain them nowhere as they are produced by Mr. Grimingham, whose remarkable 

 dexterity in the production of the radiometer bulbs is well known. He has from 

 time to time made them for me, in various forms, and in a manner that leaves 

 nothing to be desired. The principle of the apparatus is one that was adopted 

 jointly by Dr. Drysdale and myself in the study, still proceeding, of the bacteria. 

 But the forms of the apparatus, as described above, were made for these present 

 investigations. 



