114 



BACTERIOLOGY. 



one test-tube is drawn out into a long narrow neck 

 1 cm. in diameter and about 5 cm. in length. Three 

 or four points on the side of the tube are softened in 



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 t 

 blood-serum collected in bottom of second tube. 



the flame of a blowpipe, and the softened glass driven 

 inward by means of a piece of pointed wood. This 



