SECRETIONS AND EXCRETIONS. 



237 



tip or the lobe of the ear. After carefully drying, prick 

 it with a needle previously sterilized by heating over a 

 lamp or gas flame and allowed to cool. Allow five or 

 more large drops of blood to dry on the inner surface of 

 a piece of paper. Replace the folded paper in the en- 

 velope, and return to the laboratory." Where a glass 

 slide or a thin sheet of metal is used in place of the 



Fig. 29. — Application of the Serum-reaction to Typhoid Bacilli. (Williams.) 

 A, shows the distribution of the bacilli before the reaction. B, shows clump- 

 ing of the motionless bacilli after mixture with the serum of a case of typhoid 

 fever. (Diagrammatic.) 



paper, the directions for the collection of the blood 

 specimens do not differ materially from the above. 



As a rule the Widal reaction is not given by the blood 

 in typhoid fever before the sixth or seventh day, and 

 sometimes not until almost the end of the sickness; for 

 this reason it is advisable to prepare a second specimen 

 of the blood after a few days in case the first specimen 



