188 METHOD OF CULTIVATING MICRO-ORGANISMS ON POTATOES, 



Yet there remain still some inconveniences which relate to the 

 use of such reservoirs for the slices of potato, and which would 

 seem to leave an improvement in this direction to be desired. 



I would now recommend a method that recently yielded quite 

 satisfactory results, when I was, some time ago, on a short 

 stay in the Coast Hospital at Little Bay, near Sydney, where I 

 was principally engaged in making a series of cultivations from 

 dejections in cases of typhoid fever, and from organs of persons 

 who died of this disease. 



I take a number of shallow but spacious test-tubes, of about 

 10"5 cm. height by 2-5 cm. diameter, which, having been supplied 

 with a sufficiently deep cotton-wool stopper (figs. 1, 2), are then 

 sterilised in the usual manner. The preparation of the potatoes 

 is the same as in Esmarch's process. The potato-slices, cut out 

 ■of medium-sized, oval-shaped, perfectly healthy potatoes, and 

 about 1 cm. thick {jj in fig. 1, front view; in fig 2, side view ; both 

 natural size), are now placed, by aid of a clean pair of forceps, in 

 the above described test-tubes, to the width of which they are 

 made to fit. It is only advantageous if the slices press loosely by 

 one or some points of their margin on the inner walls of the 

 glass-tubes, and thus, resting either nt the bottom of these or a 

 little separate from it, they are sufficiently fixed inside those glass- 

 vessels. Then comes the steam-sterilisei', in which they remain for 

 about 1 hour at 212° F. (100° C); the potatoes are hereafter 

 thoroughly boiled and sterile. 



It is evident that in this way we arrive at a culture-medium 

 which, as regards simplicity in its manipulation, convenience in 

 the process of inoculating, and safety in keeping the desired pure- 

 culture uncontaminated during the course of examination and 

 observation, shares the same advantages with the nutrient 

 gelatinous substances and coagulated blood-serum, or with any 

 culture-soil kept in glass-tubes. A desiccation of the surfaces of 

 the potato-slices will not so soon make its appearance ; as after 

 boiling in the steam-steriliser there is at the bottom of the 

 •culture-tubes a quantity of fluid large enough to keep the contents 



