v.j METHODS OF INOCULATION. 29 



platinum wire for taking up the material to be used for inocu- 

 lation, is resorted to if one has to deal with the culture of solid 

 nourishing material, on or in which the organisms are growing 

 that we want to transplant either for inoculation of a new tube 

 or of an animal. A useful method, which does not require 

 the lifting out of the plug at all, and which can easily be 

 employed in the last case, is this : deposit from the pointed end 

 of a capillary pipette a droplet of some sterile fluid (broth or 

 thoroughly boiled saline solution) on the spot of the solid 

 medium on which the organisms are growing, then scratch this 

 spot with the end of the capillary pipette in order to get the 

 organisms off from the solid basis and mixed with the drop of 

 fluid deposited there, then let this drop again ascend into the 

 end of the capillary pipette, and withdraw this altogether. All 

 this can be done without lifting out the cotton-wool plug of the 

 test-tube or flask in which the growth is proceeding. 



If one has to use a particle of tissue the surrounding portions 

 of which are probably contaminated by putrefactive organisms, 

 e.g. a tubercle in the lung or a tubercle in the spleen, it is well 

 to follow Koch, and to disinfect the surrounding parts by just 

 washing them with a dilute solution of corrosive sublimate, and 

 then to remove these parts with clean scissors so as to obtain 

 the central particle which one wishes to use for inoculation : 

 of course one must not steep the whole organ in sublimate 

 solution, since this would naturally destroy all organisms. 



All these methods can be easily modified according to the 

 requirements of the special cases, and it is not necessary here 

 to give more than what has already been described in the 

 preceding. 1 



In order to observe in a microscopic specimen the gradual 

 changes in the growth of a micro-organism, there are several 

 methods employed. In all of them it is of course necessary to 

 keep the specimen heated up to the desired temperature. 



The simplest method consists in sowing the organisms on a 

 suitable nourishing material in a small glass cell, fit to be 

 placed on the stage of a microscope and to be there observed 

 even with high powers, similar to those cells which Koch has 

 used in his studies on bacillus anthracis. Such a glass cell 

 consists of a glass slide, in its centre a concave pit, not too 

 large, and capable of being quite closed up by an ordinary 

 cover-glass, the edges of which fasten by means of clean paraffin 

 or olive oil. Place with a clean needle a speck of spleen pulp 



1 Compare also Koch, Untersuchungen uber pafhogtne Bacterien, w Bericht* 

 mi* dem k. Gesundheitsamte, Berlin, 1881 ; and Die Aetiologie d. Tuberculose, 

 Berlin. Win. Wochentchrjft. No. 15, 1882. 



