36 A MANUAL OF BACTERIOLOGY 



steriliser for an hour or so. By this device the 

 blades are not injured. 



For the preparation of solidified sterile blood 

 serum two pieces of apparatus are necessary ; these 

 are represented in Figs. 12 and 13. Fig. 12 is the 

 serum steriliser, and consists of a double-walled 

 cylinder, 13 inches in height and 11 inches in dia- 

 meter, made of stout tin, with a copper bottom. 



FIQ. 13. SERUM INSPISSATOK. 



This cylinder is provided with a double-walled lid, 

 having a tubular prolongation of stout copper, tap, 

 and gauge : the whole being surrounded with thick 

 felt. The apparatus is divided internally into four 

 compartments ; and into these are placed the test- 

 tubes, or glass capsules, containing the blood serum. 

 Between the two walls of the cylinder is a layer of 

 water, which is heated from below ; while the water 



