Hi.] VESSELS, ETC., USED IN CULTIVATIONS. 29 



inch each, are used for the plugging of the flasks and test- 

 tubes. An assertion such as that made by Dr. Williams at 

 the British Association (Biological Section, September 1883), 

 that cotton-wool plugs are not reliable, because 

 they do not protect the fluids in the vessels 

 plugged with them from accidental air-contami- 

 nation, is to be accepted only as applying to 

 very loose plugs and to cotton-wool not properly 

 sterilised. To good firm plugs of sterile cotton- 

 wool it evidently cannot apply, since all the 

 results of all workers in this field (Pasteur, 

 Sanderson, Cohn, Koch, Klebs, Buchner, and 

 many others) are against it. 



Instruments^ such as the points of needles, and 

 forceps, used in the processes of cultivation, lift- 

 ing up cotton-wool plugs, making cotton-wool 

 plugs, inoculations, &c., must be heated in the 

 open flame of a Bunsen burner, if they are to 

 be absolutely relied on for cleanliness. Scissors 

 and knives used for cutting tissues which are 

 intended for inoculation, ought to be likewise 

 scrupulously clean. One ought to keep a 

 special set of instruments, the blades of which 

 are capable of being heated in the open flame 

 without being spoilt. 



Syringes used for cutaneous, subcutaneous, or 

 other inoculations, ought to be capable of being 

 overheated. The ordinary Pravaz syringe of 

 vulcanite not being capable of undergoing this 

 process, Koch has devised a glass syringe 

 similar to the Pravaz syringe. I do not use any syringe for 

 inoculation, but prefer using each time a fresh capillary 

 glass pipette made just before the inoculation. Into this 



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