M'Weeney — On a Method of Preparing Schizomycetes. 163 



separately, but the complex formed by a vast number of indi- 

 viduals aggregated in pure cultivation on suitable substrata ; these 

 aggregations possessing, in almost every case — when developed 

 from an originally small number of inoculated individuals — pecu- 

 liarities sufficient to claim attention, and in many cases to ensure 

 identification without the use of the microscope. 



It is not my intention in this Paper to recapitulate the various 

 methods by which a given organism may be obtained and pre- 

 served in a state of pure cultivation. The manuals of bacteriology, 

 now so numerous, contain descriptions of the manipulations, all of 

 which are founded upon the famous plan, first conceived and 

 practically worked out by Robert Koch, and which consists in the 

 employment of transparent gelatinous substrata, solid at ordinary 

 temperatures, but capable of liquefaction at a temperature equal to 

 or beneath 100° C. I do intend, however, to describe such modifi- 

 cations of Koch's original method as are specially appropriate for 

 the production of such museum preparations as I have at present 

 in view. The substrata which have proved most valuable for this 

 purpose are 10 per cent, nutrient gelatine, nutrient agar-agar, 

 potato, turnip, and what is known as Soyka's milk-rice medium. 



The vessels ought always to be of the finest glass, and consist 

 of test tubes differing from those in common laboratory use in this, 

 that they are flattened instead of being cylindrical in shape, and 

 that they have a glass foot fused on to one end, enabling them to 

 stand without support. (Specimen shown.) Another kind of vessel 

 which has proved very useful in this class of work is a circular 

 flattened glass, shaped something like two very large and deep 

 watch-glasses fastened together, with their concavities turned 

 towards one another so as to enclose a space, which is put into 

 connexion with the external world, by the glasses being drawn 

 out at one point into a sort of spout or small tube. Lastly, there 

 are glass pots of various sizes provided with glass lids fitting 

 accurately down on to a lip cut in the exterior wall. Now, as to 

 the method of using these substrata and vessels so as to make 

 museum-specimens of the contained cultures. 



The flattened test-tubes are two-thirds filled with either nutrient 

 gelatine or agar- agar, according as the organism for the reception 

 of which they are destined, is capable of growing at temperatures 

 below 20° C, or requires to be incubated at 37°. It is a matter of 



SCIEN. PROC. K.D.S. VOL. VII. PART. III. P 



