The Life of the Fly 



The value of chemist's pepsin is estimated 

 by the quantity of hard-boiled white of egg 

 which a gramme of that agent can liquefy. 

 The mixture has to be exposed in an oven to 

 a temperature of 140° F. and also to be fre- 

 quently shaken. My preparation, in which the 

 Bluebottle's eggs are hatched, is neither 

 shaken nor subjected to the heat of an oven; 

 everything happens in quietness and under the 

 thermometrical conditions of the surrounding 

 air; nevertheless, in a few days, the coagu- 

 lated albumen, treated by the vermin, runs like 

 water. 



The reagent that causes this liquefaction 

 escapes my endeavours to detect it. The 

 worms must disgorge it in infinitesimal doses, 

 while the spikes in their throats, which are in 

 continual movement, emerge a little way from 

 the mouth, re-enter and reappear. Those 

 piston-thrusts, those quasi-kisses, are accom- 

 panied by the emission of the solvent: at least, 

 that is how I picture it. The maggot spits on 

 its food, places on it the wherewithal to make 

 it into broth. To appraise the quantity of the 

 matter expectorated is beyond my powers : I 

 observe the result, but do not perceive the 

 leavening agent. 



344 



