58 



PHYSIOLOGICAL RELATIONS 



very careful work purified beeswax and white vaseline should be 

 used. As a matter of convenience, two rings are usually cemented 

 to the same slip. To make the cells, the wax is kept melted, the 

 slide is slightly heated in the flame, and by means of the forceps 



the ring is passed through the 

 flame, after which one edge 

 is dipped lightly into the 

 melted wax, then quickly 

 placed upon the slip. If the 

 wax is too hot, it will be nec- 

 essary to touch the ring sev- 

 eral times to the melted wax, 

 then raise it high enough to 

 cool somewhat. When the 

 wax is cool the free edge of 

 the cylinder is provided with 

 a ring of vaseline by invert- 

 ing the cell over a slip, or 

 shallow watch crystal, upon 

 which there is spread a thin 



layer of melted vaseline (Fig. 

 Fig. 12. Stand and Dish for Beeswax , t-,, ,, , ,j i 



12). The cell should be 



momentarily held in this inverted position, or rested in this position 



on a rack, in order that the ring of vaseline will have some depth. 



By means of the vaseline ring the cover is, at the proper time, 



cemented firmly to the glass cylinder. If the temperature at which 



the cultures are to be incubated differs considerably from that at 



which the cells are made, it has been found well to make with 



the back of a scalpel a small nick in the vaseline ring, through 



which nick the expanding air may pass when the cultures are 



placed in the thermostat, or culture incubator. Afterwards they 



may be permanently sealed by slight pressure with scalpel or 



needle. A drop of the culture fluid to be used is placed on each 



cover glass, and about half a dozen drops of the same fluid are 



placed in the bottom of the cell. A small glass rod is the only 



satisfactory dropper for the first-mentioned work. The drops are 



inoculated with a few spores by means of a platinum needle, 



massing or bunching of the spores being prevented as much as 



