136 



BACTERIOLOGY 



about 5 cm. in length. Three or four points on the side of 

 the tube are softened in the flame of a blowpipe, and the 



FIG. 20 



Rivas apparatus for collecting blood serum: A, long narrow neck on 

 first tube; B, constriction on tubes near mouth; C, invaginations on first 

 tube; D, small cannula drawn out on extremity of first tube; E, blood- 

 clot, and F, blood serum collected in bottom of second tube. 



softened glass driven inward by means of a piece of pointed > 

 wood. This gives supports on the interior of the tube to 



