METHODS OF CULTIVATION OF BACTERIA. 



first blood which flows, and which may be contaminated from 

 the hair, etc., to escape ; fill the vessel with the blood sub- 

 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 successive 

 days. It is always well to incubate it for a day at 37 C. 

 before use, to see that the result is successful. After 

 sterilisation it is then "inspissated," by which process a 

 clear solid medium is obtained. " Inspissation " is prob- 

 ably 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 ap- 

 paratus 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 containing 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 



FIG. 8. Blood serum inspissator. 



