2i6 Cultures, and their Study 



not much practical value has come of it. It can be done by warming 

 the glass of the tube sufl5ciently to permit the gelatin containing the 

 growth to be removed in a lump and placed in Miiller's fluid (bichro- 

 mate of potassium 2-2.5, sulphate of sodium i, water 100), where it 

 is hardened. When quite firm it is washed in water, passed through 

 alcohols ascending in strength from 50 to 100 per cent., embedded 

 in celloidin, cut wet, and stained like a section of tissue. 



Winkler* accomphshes the same end by boring' a hole in a block 

 of parafl&n with the smallest size cork-borer, soaks the block in bi- 

 chlorid solution for an hour, pours liquid gelatin into the cavity, 

 allows it to sohdify, inoculates it by the customary puncture of the 

 platinum wire, allows it to develop sufficiently, and when ready 

 cuts the sections under alcohol, subsequently staining them with 

 much diluted carbol-fuchsin. 



Museum Culture Preparations.^Neat museum specimens of plate 

 and puncture cultures in gelatin can be made by simultaneously 

 killing the micro-organisms and fixing the gelatin with formaldehyd, 

 which can either be sprayed upon the gelatin or apphed in dilute 

 solution. As gelatin fixed in formaldehyd cannot subsequently be 

 liquefied, such preparations will last a long time. 



Standardizing Freshly Isolated Cultures.^ — This is a matter of 

 some importance, as in bringing bacteria into the new environment 

 of artificial cultivation their biologic peculiarities are temporarily 

 altered, and it takes some time for them to recover theriiselves. 

 While the appearances of the freshly isolated organism should be 

 carefully noted, too much stress should not be laid upon them, and 

 before beginning the systematic study of any new organism it should 

 be made to grow for several successive generations upon two or 

 three of the most important culture media. Its saprophytic exist- 

 ence being thus estabhshed, the characteristics manifested become 

 the permanent peculiarities of the species. 



* " Fortschritte der Medicin," 1893, Bd, xi, No. 22. 



