Thermal Death-point of Monai Germs. By W. H. Dallinger. 3 



This was done very carefully on a large series of glass slips for 

 each of the six forms of monads whose life-history had been worked 

 out. By this means it was shown that the thermal death-point was 

 not a fixed one, but that it varied with the forms. Taking, how- 

 ever, an average or mean of the results presented by the whole six, 

 it was seen that the germs could resist the destructive action of 

 heat better than the adult in the proportion of 11 to 6. In short, 

 they possess nearly double the capacity for resisting heat.* 



Now I felt at the time these experiments were being made, and 



tact with the edge of the air space between the " cover " and the slip of glasti 

 containing the germs that had been exposed to heat, the fluid is withdrawn from 

 the tube to the space between the two glass surfaces where the fluid is needed, 

 because of the greater capilLiry attraction of the latter. If these fine glass tubes 

 of pabulum be kept in absolute alcohol, and the whole process be manipulated 

 rapidly and firmly, the least conceivable danger of the communication of any form 

 of minute life is secured ; but certainly not absolute freedom from tlie possibility. 

 But in this instance it is not needful that such certainty should exist ; only the 

 development of a known set of germs, in a known position, and with a known 

 developmental history, is being studied — and this repeatedly before any conclusion 

 could be arrived at ; and therefore although it would be a benefit to exclude a 

 great accession of other forms, it was not absolutely necessary. 



* In a paper on " The Conditions favouring Fermentation," &c., read before 

 the Linneau Society, Dr. Bastian refers in a most perplexing way to these experi- 

 ments. He entirely misunderstands them. He desires to show that the evidence 

 these experiments yield is " contradictory," and to this end attempts to tabulate, 

 in a manner peculiarly unsatisfactory to the discovery of what our facts were 

 intended to show, what he calls "the results." In doing this he distinguishes 

 between spores and sporules, a distinction nowhere made in the papers in question. 

 These words, witli others, such as germ, germule, &c., were employed, as they had 

 been by other investigators, synonymously. They all referred to a minute 

 organic product, giving rise bj development to a known organic form : this is 

 manifest enough upon tlie surface, for nowhere is any attempt to distinguish one 

 from the other made ; and as the papers were written at intervals, quite distinct 

 from each other, it was natural enough that the same word in meaning, although 

 perhaps not in f(jrm, should be used. And this is the fact. It is plain, then, that 

 in seeking to set \i\> an unwarranted distinction between what is in every case the 

 same thing, our critic is introducing error of the most confusing kind. But 

 beyond this, and of yet more importance, is the fact that he tabulates the results, 

 as though the various temperatures to which the sporules, spores, germs, or what- 

 ever other name these minute genetic products may be called, were exposed, u-tve 

 the same for all the forms, and that therefore the variety of results points to 

 uncertainty. In reality, however, as a careful reading of the papers will show, 

 the variety of results is dependent on the various heat-resisting capacity of the 

 specific forms stmlied separately. Dr. Bastian has therefore changed the separate 

 details of heat-condition for each monad into one generic " table," lieaded " Nature 

 of Heat p]xpoHure." Then throwing the details all together, and introducing a 

 distinction between "spores" and "sporules," he gets at results which do not 

 present enough " unity of results" for the " uniformity of conditions" employed. 

 Tills is not surprising. But it sliould be observed at the same time, that " imity 

 of result" in a large series of experiments on such delicate vital subjects, under 

 Bucb complex and difficult circumstiinces, is scarcely to be looked for by those 

 who only claim the use of ordinary powers in the projection and carrying out of 

 experiments. Indeed, under such circumstances, it may be fairly suspected that 

 "unity of result" implies the possibility of unity of error. If the results of 

 investigation bad been very much more diverse than they are (and they present 

 no aj>proach to the diversity Dr. Bastian's doubtless unwitting erri»r of inter- 

 pretation would involve), this would not vitiate them, for the inference is made 

 not from the nojntivc but from the }>ositivc results in every case. 



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