AND PHYSIOLOGY. 



397 



ratner than some other part of the ear, and also the value of 

 the three small bones of the ear, at one extremity fastened to 

 the drum and at the other by cartilages to the semicircular 

 canals. Other experiments also showed that a solid body of 

 the form of the stapes alone was the best to communicate with 

 the auditory nerve. 



725. Function of the Cochlea and Semicircular Canals. 

 — It has been thought by some that the cochlea enables one 

 to determine the pitch of sound, since animals which possess 

 the fullest development of this organ have the largest range 

 of voice. Another speculation is, that the semicircular canals 

 aid in the determination of the direction from which sounds 

 come, since in animals where they exist, they are always 

 placed at right angles to each other. 



725 a. Three Physical Properties of Sound— The three 

 physical peculiarities of sound are intensity or loudness, pitch 

 or length of the waves, and quality, or the difference between 

 the same note on a flute and violin, although equal in intensity 

 and pitch. And a theory has been proposed, substantiated by 

 many facts, that the membrana tympani enables us to deter- 

 mine the intensity, the cochlea the pitch, and the semicircular 

 canals the quality of sound. 



THE SENSE OF HEARING IN ANIMALS. 



726. External Ears — Semicircular Canals— Cochlea— 

 Os Qua dr alum. — All mammals, as a general rule, have ex- 

 ternal ears. These, in some animals, like the bat, are enor- 

 mously developed in proportion to the dimensions of the body. 

 Besides, in several genera they can be turned in any direction 

 the animal may choose. In man the ear consists of but one 



725. What suggestion has been made of the use of the cochlea and semicircular canals? 

 725 a. What are the three physical peculiarities of sound ? 726. What mammals have 

 external ears? "What is said of them in the bat? How many pieces has the pinna in 

 most animals ? 



