46 MICRO-ORGANISMS AND DISEASE. [CHAP. 



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 with- 

 out 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 



1 Compare also Koch, Untersuchungen iiber patJiogene Bacterien, in 

 Berichte aus dem k. Gesundheitsamle, Berlin, 1881 ; and Die Aetiologie 

 d. Tuberculose, Berlin, klin. Wochenschrift, No. 15, 1882. 



