20 MICRO-ORGANISMS AND DISEASE. [CH. in. 



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 inocula- 

 tions, 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 pipette I draw the 

 droplet to be used for inoculation, and having made a very 

 small incision about of an inch through the skin, the 

 pointed end of the pipette is pushed forward into the sub- 

 cutaneous tissue for about half an inch or one inch and then 

 the fluid is blown out into the tissue. In this way I am 

 always absolutely safe from any contamination with a pre- 

 viously used virus, which might possibly adhere to one or other 

 part of a syringe. 



The fine point of capillary pipettes (Fig. 5), used for in- 

 oculation of animals, or for drawing out a drop of fluid of a 

 cultivation in a flask or test-tube, or for inoculating material 

 contained in a test-tube or flask, are thus made: while one. 

 hand holds the bulb of the pipette, the other holds one end, 

 and putting at some distance from this end the tube into an 

 ordinary flame and quickly drawing it out, a point of extreme 

 fineness can be made. The same is done with the other end. 

 Such a pipette can be considered as practically closed at both 

 ends. 



