98 



MANUAL OF BACTERIOLOGY. 



Smears of blood are prepared as follows: Have two perfectly 

 clean, square cover-glasses. The finger, or the lobe of the ear, 

 having been carefully washed with water, alcohol and ether, is 

 punctured with a sterilized needle, and a small drop of blood 

 issues which is wiped away with a clean cloth. The second 

 drop of blood should be taken ; it should be about the size of a 

 pin's head. No pressure should be exerted upon the skin. 

 This drop of blood is placed on one of the cover-glasses. The 

 other cover-glass is laid upon the first, both being handled with 

 forceps. The drop of blood becomes flattened out into a thin 

 film. Immediately and before the blood has had time to 

 coagulate the two are sHpped or shd away 

 from each other in a horizontal plane, not 

 forcibly pulled apart. In this way the 

 blood will be spread in thin films on the 

 cover-glasses. It is best to place the 

 cover-glasses so that one does not cover 

 the other exactly, but so that the sides of 

 the one lie diagonally to the sides of the 

 other, although their centers coincide (Fig. 

 37). Films of blood which are to be 

 examined for the parasite of malaria may 

 be prepared in this manner. Samples of blood to be used for 

 the serum reaction for typhoid fever need to be good-sized 

 drops of blood, which may be collected on cover-glasses or 

 pieces of unsized paper and allowed to dry. To test 

 blood by culture methods, i to 5 c.c. may be drawn from a vein 

 during life, using a steriHzed hypodermic syringe and all anti- 

 septic precautions. The blood thus taken may then be used 

 for cultures in various ways. A good method for general pur- 

 poses is to empty the syringe quickly into a flask holding 100 

 c.c. or more of bouillon or dextrose-bouillon. The mixture of 

 blood and bouillon should be placed in the incubator for one to 

 two days. If the bacteria develop, they may be secured in pure 



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Fig. 37. — Manner OF 

 Placing Cover- 

 glasses IN Mak- 

 ing Films of 

 Blood. — {A Iter 

 Cabot.) 



