TEST-TUBES 



25 



4. After cooling, it is filed through at an appropriate place, being 

 careful to leave a somewhat long stem (Fig. 7). 



5. The open end may now serve as a funnel for filling the bulb. 



6. The bulb is now sealed by warming the air above the level of the 

 fluid and then sealing the tip. With a long stem, in order to secure a 

 portion of the contents, the sealed end may be broken off from time to 

 time; it is readily resealed. 



7. Instead of this procedure the fluid may be placed in the test- 

 tube at once, the upper end being heated in the usual manner and drawn 

 out; the stem is broken through, and the tip sealed. If the tube is 

 small or the contents are such as will almost fill a tube, this method may 

 not be successful, owing to the production of steam on heating the 



FIG. 7. METHOD OF MAKING A LARGE VACCINE AMPULE OF A TEST-TUBE. 



fluid, which either cracks the bulb or causes the tip to explode at the 

 time of sealing. % 



TEST-TUBES 



1. In this work test-tubes of various sizes are used mainly for mak- 

 ing the agglutination, precipitin, complement fixation, and other tests. 

 They should be made of good glass, with round bottoms, and be well 

 annealed. 



2. Test-tubes should be thoroughly clean, clear, and sterilized, pref- 

 erably by dry heat. It is not necessary to plug them with cotton unless 

 they are to be used for bacteriologic work, for when a large number of 

 tubes are used, this is a waste of time and of material. If the tubes are 

 to be used within from twenty-four to forty-eight hours, merely plac- 

 ing the tube mouth end downward in the wire basket is sufficient. A 



