COLLECTION OF MATERIAL. 



water, alcohol, and ether, is punctured with a sterilized 

 needle, and a small drop of blood issues which is wiped 

 away. 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 

 slipped or slid away from each other in a horizontal plane, 

 not forcibly pulled apart. The blood, therefore, 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 ex- 

 actly, 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 pretty good- 



ij r ut j u- u u Manner of Placing 



sized drops of blood, which may be col- cover-glasses in Mak- 

 lected on cover-glasses or pieces of un- ing Films of Blood, 

 sized paper and allowed to dry. To (After Cabot.) 

 test blood by culture methods, i to 5 c.c. may be drawn 

 from a vein during life, using a sterilized hypodermic syringe 

 and all antiseptic precautions. The blood thus taken may 

 then be used for cultures in various ways. A good method 

 for general purposes 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 cultures by plating, 

 and may be studied further, as the occasion requires. 



