BLOOD SERUM, 



sequently shed. Carry carefully back to the laboratory 

 without shaking, and place for twenty-four hours in a cool 

 place, preferably an ice chest. The clear serum will 

 separate from the clotted blood. With a sterile 10 c.c. 

 pipette, transfer this quantity of serum to each of a series 

 of test-tubes which must previously have been sterilised by 

 dry heat. The serum may, with all precautions, have been 

 contaminated during the manipulations, and must be 

 sterilised. As it will coagulate if heated above 68 C, 

 advantage must be taken of the intermittent process of 

 sterilisation at 57 C. 



(method B (4)). It is 

 therefore kept for one 

 hour at this temperature 

 on each of eight succes- 

 sive days. It is always 

 well to incubate it for a 

 day at 37 C. before use, 

 to see that the result is 

 successful. After steri- 

 lisation it is " inspis- 

 sated," by which process 

 a clear solid medium is 

 obtained. " Inspissa- 

 tion " is probably an 

 initial stage of coagulation, and is effected by keeping 

 the serum at 65 C. till it stiffens. This temperature 

 is just below the coagulation point of the serum. The 

 more slowly the operation is performed the clearer will be 

 the serum. The apparatus used is seen in Fig. 8. It 

 consists of a rectangular, shallow, covered, hot-water jacket, 

 which can be rapidly heated by an S-shaped Bunsen con- 

 taining many lateral perforations, from each of which a 

 flame issues. The apparatus rests on four legs, the front 

 two of which can be shortened, and thus the whole tilted 

 forward. Tubes containing a suitable quantity of serum 

 can thus be laid on their sides without the contents reach- 

 ing as high as the plug. The serum tubes being thus 



FIG. 8. Blood serum inspissator. 



