390 Proceedings of the Royal Physical Society. 



By using flasks, the necks of wliicli are the same size as 

 the bore of the test-tube, the action of gases on micro- 

 organisms may be determined ; and with other slight modifi- 

 cations, which are at once apparent, the method may be 

 adapted for the action of heat, modified or increased pressure 

 conditions, and so on. So far, I have had extensive experi- 

 ence of the use of the method with fluids only, but that 

 has been in all cases most satisfactory. The small number 

 of experiments where gases, heat, etc., have been employed, 

 have, however, given most encouraging results. 



Explanation of Plate XVIII. 



Fig. 1. Glass rod, with platinum wire and thread (c) attached to loops {d, d). 



Fig. 2. Test-tube containing nutrient jelly, into which is introduced the 

 glass rod («) surrounded by jplug of cotton wadding {h). Fused into the end 

 of the rod is the platinum needle (c), with a couple of loops (rf, d), to which 

 are attached the ends of silk thread by single knots. 



