238 INFECTIOUS AND PARASITIC DISEASES. 



proves negative. In about five per cent of the cases the 

 reaction is never obtained during the whole course of 

 the disease, a fact, it would appear from recent studies, 

 due to the presence, as causative factor in the disease, 

 of another bacterium, the para-colon bacillus. Blood 

 from such a case when tested with a para-colon bacillus, 

 gives the characteristic reaction. 



For the detection of the malarial parasites 



Malaria, either glass slides or cover-glasses are used, 

 the former being given the preference by the 

 majority of municipal laboratories. The directions for 

 preparing specimens of blood in suspected malarial 

 fever as given by the New York Health Department, 

 are as follows: 



"Wash two glass slides with alcohol, and wipe with 

 a soft, clean linen cloth (not a soiled handkerchief) 

 until clean and shiny. On cold, damp days the slide 

 should be warmed over a flame. After cleaning, the 

 slides must be held by the sides (FF in diagram), and 

 surfaces and ends not touched. Clean the patient's 

 ear-lobe with alcohol and prick the skin with a sterile, 

 surgical needle or a small pointed scalpel, so as to act- 

 ually incise the capillaries. The blood should not be 

 squeezed out, but should flow freely. Wiping off the 

 first few drops, the third or fourth drop should be 

 quickly (before it gets much larger than a pin head) 

 taken up on the edge of one end of one slide. Place 

 this edge on the surface of the other slide, as indicated 



