172 LEISURE-TIME STUDIES. 



destruction of any living particles contained in the fluid 

 itself. Isolation and destruction are the two chief ideas 

 involved in such experiments ; and it may be freely admitted 

 that, if both of these conditions be perfectly carried out 

 in any experiment, such procedure may be deemed a crucial 

 test, and the results so obtained may be regarded as of 

 stable and satisfactory kind. But to procure the perfect 

 isolation of the fluid, and the complete annihilation of 

 germs, hie labor, hoc opus est. The very nature of the ex- 

 perimentation renders it an exceedingly difficult matter to 

 ensure that either condition is perfectly carried out. The 

 manipulation involved is of the most delicate kind, and the 

 sources of error are not only singularly numerous, but are 

 also difficult of detection. An undetected flaw or crevice 

 in the apparatus, a moment of inattention on the part of 

 the experimenter, and the results of a whole series of ex- 

 periments may be unwittingly vitiated. So that, although 

 the conditions aimed at are themselves perfectly clear and 

 denned, their perfect attainment forms one of the most 

 difficult tasks which the modern investigator can have set 

 before him. 



On being first published, some years ago, Dr. Bastian's 

 experiments naturally attracted the attention of the bio- 

 logical world, and revived a controversy which had, to say 

 the least, been in a smouldering condition for some time 

 previously, and which, moreover, in the minds of many 

 observers, had been regarded as practically settled in favour 

 of the germ theory, and of biogenesis at large. The facts 

 asserted by Dr. Bastian, dealing with a problem of such 

 important nature, were not of course to be tacitly accepted 

 by scientists, or without due questioning and verification 

 at the hands of independent observers. Accordingly, Dr. 

 Bastian's experiments were repeated by other physiologists, 

 the method of procedure respecting Bastian's mode of pro- 

 cedure being thus detailed by Dr. Burdon Sanderson. An 

 infusion of turnip was prepared and divided into two 

 portions, one portion being neutralised to correct its acidity 



