186 THE POPULAR SCIENCE MONTHLY. 



is altogether another question when we have to decide whether moist 

 Bacteria or their germs are endowed with this seed-like property of 

 developing after desiccation. To maintain his position, Spallanzani 

 was compelled to assume that they did possess this potentiality. 

 Modern science, however, on the basis of experiment, declares that 

 they have no such property. We are told most unreservedly by Prof. 

 Burdon-Sanderson, 1 not only that "the germinal particles of micro- 

 zymes (Bacteria) are rendered inactive by thorough drying without 

 the application of heat," that is, by mere exposure to air for two 

 or three days at a temperature of 104 Fahr., but also that, "fully- 

 formed Bacteria are deprived of their power of further development 

 by thorough desiccation." Thus is the most important assumption 

 made by Spallanzani swept away, and with it all the strength that 

 his position may have appeared to possess. Neither he, nor any of 

 his followers, can hope to save their germs from the full action of heat 

 by assuming the preexistence of a protective desiccation, when they 

 are told, on the unquestionable authority of Prof. Sanderson, that such 

 desiccation would be in itself destructive to them. 



We are left, therefore, now face to face with only one other ques- 

 tion. Has the progress of science, it may be asked, since the time of 

 Spallanzani, in any way tended to strengthen the possibility that Bac- 

 teria-germs or any forms of living matter in the moist state can resist 

 the destructive action of boiling water, even for two or three minutes ? 

 And to this question a negative answer may be unreservedly given, 

 since the progress of science has shown, on the contrary, that such a 

 supposition becomes more and more improbable in the light of all un- 

 complicated investigations bearing on the subject. To these results 

 of modern research I must now call the reader's attention. 



In the first place, the specific question with which we are more im- 

 mediately concerned, as to the thermal death-point of Bacteria and 

 their germs, has itself been answered by most decisive experiments. 

 As the writer has elsewhere already shown, 2 all direct experimentation 

 on this subject leads to the conclusion that Bacteria and their germs, 

 whether visible or invisible, are killed by a brief exposure to a heat 

 of 140 Fahr. in the moist state. Thus Dr. Sanderson's experiments 

 having proved that the germs of these organisms are, as regards their 

 ability to withstand desiccation, related to eggs rather than to seeds, 

 the writer's own experiments tend to strengthen this resemblance by 

 showing that these Bacteria-germs also (like the eggs with which Spal- 

 lanzani experimented) are invariably killed at a temperature of about 

 140 Fahr. 



Although, therefore, my experiments are not favorable to Spallan- 

 zani's assumptions, they are entirely in accordance with his experi- 

 ments. The thermal death-point ascertained by him for the eggs of 



1 " Thirteenth Report of the Medical Officer of the Privy Council," p. 61. 



2 "Proceedings of Royal Society," 1873, No. 143, p. 224, and No. 145, p. 325. 



