160 THE HOUSE I LIVE IN. 



Some suppose that it enables us to hear a 

 little through the mouth ; but this is not prob- 

 able. If we hear at all through the mouth, it 

 is in a degree scarcely worth mentioning. 



Near the hinder part of this cavity of the 

 tympanum there is also an opening into a col- 

 lection of cells in the bone. The bones in 

 which these cells are situated may be found 

 quite prominent behind the ear. The use of 

 the cells is not very well known. 



Though the ear is to be considered a door 

 of the human habitation, the passage in it, as 

 we have seen, is usually closed by the ear 

 drum. The door-way for everything except 

 sound, would, therefore, be more properly 

 through the mouth. 



Sometimes we know not how the drum 

 membrane gets broken. Men have been 

 found, for example, who could force tobacco 

 smoke, held in their mouth, out at their ears. 

 This proves that the membrane in question 

 must have had a hole in it. I do not know 

 that this affects the hearing very much. It is 

 true it requires us to be more cautious what 

 we get into our ears, for if substances get 

 beyond the ear drum quite into the cavity of 



