122 BACTERIOLOGY 



precautions should be noted, viz.: The solidification of the 

 serum in the dry air sterilizers must be complete, else its 

 surface will be rough and broken by bubbles; the same 

 results if the temperature in the dry air sterilizer is brought 

 up too rapidly. 



Serum prepared in this way is neither clear nor colorless. 

 This is ordinarily not a disadvantage. The popularity of 

 the method is due to its simplicity, the rapidity with which 

 a satisfactory serum may be prepared and especially to 

 the fact that the rigid precautions against contamination 

 observed in the older methods, where sterilization at low 

 temperature was practised, are not essential to success, 

 since even though such contaminations occur they are 

 eliminated by the high temperatures used in this procedure. 



Blood-serum from Small Animals. — For special purposes 

 it is often desirable to secure blood serum under strictly 

 aseptic precautions from particular species of animals, 

 many of them being small. To this end .there have been 

 devised a number of handy methods. That which in our 

 hands has proven the simplest and generally most useful 

 is the Rivas modification^ of Latapie's method. It is as 

 follows: 



The Rivas apparatus is constructed from two test-tubes 

 about 15 X 180 mm. in size. The mouth of 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 the flame of a blowpipe, and the 

 softened glass driven inward by means of a piece of pointed 

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

 hold the coagulated blood in place. Between the long 

 narrow neck and the body of the tube a constriction is 



' University of Pennsylvania Medical Bulletin, 1904, vol. xvii, p. 295. 



