3n 



holes the steamy and scented breath of the beaver 

 inhabitants within. Since the ventilation of beaver 

 houses is exceedingly poor, and as this animal 

 probably does not suffer from tuberculosis, it is 

 possible that ventilation is assisted, and some 

 of the impure air absorbed by the water, which 

 rises almost to the floor in the large entrance- 

 holes. 



The early trappers from time to time noted 

 extended general movements or emigrations 

 among beaver, which embraced an enormous area. 

 They, as with human emigrants, probably were 

 seeking a safer, better home. Some of, these move- 

 ments were upstream, others down; commonly 

 away from civilization, but occasionally toward 

 it. For this the Missouri River was the great 

 highway. Limited emigrations of this kind still 

 occasionally occur. 



The annual migration is a different affair. This 

 has been noted for some hundred and fifty years 

 or more, and probably has gone on for centuries. 

 This peculiar migration might be called a migra- 

 tory outing. In it all members of the colony 

 appear to have taken part, leaving home in June, 

 132 



