163 



during the whole course of our existence ;* while others are as re- 

 markable for their tardiness of growth as these are for their rapidi- 

 ty. -f- In the present state of our knowledge of the physiology of these 

 organs, I am afraid we cannot offer any satisfactory explanation of 

 the final cause of this phenomenon. As, however, a knowledge of 

 the changes, which an organ undergoes at different periods of life, 

 constitutes an important portion of that series of data required, before 

 we can hope to form any rational theory of the manner in which it 

 performs its functions, we should collect industriously, and note with 

 accuracy, every fact connected with the development of these ca- 

 vities, although we may not be able, at present, to apply them to 

 any very useful purpose. 



• Viz. Cavity of the tympanum, groove for the membrane of the tympanum, bones of the 

 tympanum, Eustachean tube, oval hole, round hole, promontory, pyramid, cochlea, vesti- 

 bule, semicircular canals, internal auditory tube. 



f External auditory tube, mastoid cells. 



z2 



