Thermal Death-point of Monad Germs. By W. H. Ballinger. 5 



to resist the action of heat must he dependent upon the condition 

 in which it may he when submitting to that test. It is known 

 that growing or developing organisms in difi'erent stages are 

 differently affected by surrounding conditions. Thus a germinating 

 seed has less capacity to resist heat than one in which such activity 

 has not been set up. Hence it is, that from a long-continued series 

 of experiments I am convinced that it must be on the spores in 

 their freshly emitted s^a^ethat our experiments must be made if we 

 would arrive at positive results. 



Dr. Bastian says '' It would have been perfectly easy to have 

 put one or two drops of the fluid into a small tube, to have 

 hermetically sealed it, and then to have heated it for ten minutes or 

 more to different degrees before subjecting the fluid to a prolonged 

 microscopical examination upon a carefully prepared slide." * 



It is plain that however " easy " this method might have been, it 

 would have been to all intents and purposes useless. There could 

 . have beenno certainty that the spores, in the only condition serviceable 

 for experiment — that is in the freshly emitted state — would be in the 

 *' one or two drops." They might have been ; and spores in various 

 stages of development in all probabihty would have been ; but of 

 these latter we make no affirmation ; and without certainty as to 

 the former, experiment is worse than waste of time. Partly 

 developed germs almost certainly succumb at a temperature nearly 

 as low as the adult — but if the germ, before germination begins, 

 can resist any higher temperature, it is plain that we must know 

 that they are there, in the condition required, before the heating is 

 begun. And when we remember that in a given field of view 

 under the Microscope, where monads are kept alive in the moist 

 chamber stage,t that fission may be the only phenomenon dis- 

 coverable in a given form for four or six days, and that in all cases 

 the sporing condition is relatively rare, it is plain that any attempt 

 at deduction from so happy and " easy " a method as Dr. Bastiau's 

 " one or two drops " heated in a sealed tube could have led to no 

 result having the remotest scientific value. 



What is required then is some arrangement which will enable 

 us to be assured, that germs seen to be emitted from a given sac 

 are at once submitted to heat in fluid, and then that the fluid shall 

 be capable of examination for an indefinite period with competent 

 optical powers. 



The piece of glass apparatus which I am about to describe, 

 meets these necessities. It would not, however, be competent by 

 itself; it is as a supplement to the method of inquiry by dry heat, 

 that it specially serves. By that method we can follow the germ 

 after heating from its first germinal activity to its adult condition, 



* " Conditions favouring Fermentation," loc. cif., \\ 78 (note), 

 t Vide ' Moil. Micr. Journ.,' xi. p. 97, &c. 



