56 THE FLEA [CH. 



vomiting the septicsemic blood from their stomachs 

 and so transferred the plague bacillus to the puncture 

 which they made in the skin. 



But an experiment, which has been tried several 

 times, seems to show that the supposed valve is 

 effective. The stomach of a flea which had recently 

 fed was dissected out intact. As long a portion of 

 rectum as possible was left attached at the hinder 

 end. The gullet having been severed, well in front 

 of the valve, pressure was applied with a blunt tool 

 with the object of forcing the blood through the 

 gullet. The hind aperture of the stomach was, at 

 the same time, closed by pinching up the rectum. 

 The result was that, in no instance, was it possible 

 to force blood through the passage which leads into 

 the gullet. Yet sufficient pressure was applied to 

 burst the stomach. 



The stomach of a flea is a pear-shaped sack which 

 occupies an appreciable part of the insect's abdomen. 

 That it is capable of containing a comparatively large 

 amount of blood is apparent from the observation 

 that after a flea has enjoyed a good meal nearly the 

 whole of the abdomen is seen to be filled with a bright 

 red mass. During the investigation of the part played 

 by fleas in spreading plague an endeavour was made 

 to measure, as accurately as possible, the average 

 capacity of a rat-flea's stomach when filled with blood. 

 Healthy fleas, taken from Bombay rats, were starved 



