20 STUDIES IN ANIMAL LIFE. 



the cause is not to be sought in their breathing 

 filings, but in the sedentary and unwholesome con- 

 finement incidental to their occupation. Miners 

 and coal-heavers are not troubled with consump- 

 tion. Moreover, if the filings were the cause, all 

 the artisans would suffer, when all breathe the same 

 atmosphere. Secondly, while it is true that dis- 

 colored lungs have been observed in some miners, 

 it has not been observed in all or in many ; where- 

 as it has been observed in men not miners, not ex- 

 posed to any unusual amount of coal-dust. Third- 

 ly, and most conclusively, experiment has shown 

 that the coal-dust can not penetrate to the lungs. 

 Claude Bernard, the brilliant experimenter, tied a 

 bladder containing a quantity of powdered char- 

 coal to the muzzle of a rabbit. Whenever the an- 

 imal breathed, the powder within the bladder was 

 seen to be agitated. Except during feeding-time 

 the bladder was kept constantly on, so. that the 

 animal breathed only this dusty air. If the powder 

 could have escaped the vigilance of the cilia and 

 got into the lungs, this was a good occasion. But 

 when the rabbit was killed and opened many days 

 afterward, no powder whatever was found in the 

 lungs or bronchial tubes ; several patches were col- 

 lected about the nostrils and throat, but the cilia 

 had acted as a strainer, keeping all particles from 

 the air-tubes. 



The swimming apparatus of the Opalina has led 

 us far away from the little animal who has been 



