458 BACTEEIOnUOGY. 



broken off by slig'htly bending it between the fingers. The open capil- 

 lary end should now be passed several times through the flame in. 

 order to sterilize the exterior. By blowing through the tube, direct- 

 ing the stream of air against the back of the hand, one can ascertain 

 when the tube has cooled suflBciently for use. The pipette is then in- 

 serted into the test-tube or other container and the liquid is drawn 

 up by suction. The end of the tube in the mouth is closed by the 

 tongue or finger, and the pipette is then withdrawn. The liquid can 

 now be transferred to another t^ibe or to a series of tubes or flasks. 



The pipette is very useful in removing' the contents of 

 a pus cavity in an animal, in collecting an exfidate (p. 277) 

 or in drawing- blood from the heart (p. 279). It can be used 

 to remove liquid cultures or surface cultures from agar, 

 potato, etc. In the latter case, sterile water or bouillon is 

 transferred to the tube by means of the pipette. The 

 growth is whipped up to make a fine suspension which 

 then can be drawn up into the pipette. The pipette is ex- 

 tremely useful when it is desirable to inoculate a larg6 

 number of tubes; in the tests for agglutination and in the 

 preparation of sacs. It is even more useful than the plati- 

 num wire. 



The material can be kept in the tube by sealing the 

 capillary end. "If at the same time the tube is sealed below 

 the cotton plug, the culture or material can thus be kept 

 perfectly free from contamination or desiccation. It is fre- 

 quently desirable to preserve the heart-blood of an animal, 

 and thus keep the organism that may be present in its full 

 virulence. This may be done in the manner described or 

 by the following slightly modified procedure. 



A pipette is heated about a half an inch beyond where 

 it begins to narrow. When the glass has softened it is 

 drawn out about 15 cm. (6 in.). Fig. 62 a shows such a 

 pipette. The bulb and capillary is then filled to the x 

 mark according to the directions given above. The capil- 

 lary is then sealed at the end and also at the x mark. The 

 growth or blood is thus sealed in a bulb tube about 15 cm. 



