4:70 Dynamic Theory. 



als, the cochlea is spiral. In the Whale tribes and the Hedghog, the cochlea 

 makes one and a half turns. In the Paca ( a rodent) it makes five turns. 

 In the apes and man it makes two and a, half turns. The ear of man, 



Fig. 213 Ear bones of A Bat. B Shrew, Stapes or Stirrup bone of 



C Mole. D Hedgehog. .E. Marmot. /'.Sloth. 



Blood vessels running through C and E. The discs at the hottoni indicate the shape 



of the foot of the stirrup. ( Owen,) 



while more discriminating as to musical sounds than that of most other 

 animals, is far behind man}' of them in the acuteness of its perception 

 and its sensitiveness. 



The eustachian tube is 

 the remains of the first 

 gill slit in the embryo. 

 In the primitive cartilagi- 

 nous fishes, this gill slit 



remains open, and is a 

 blow-hole leading from the 

 back part of the mouth. 

 In the further develop- 

 ment of the ear in the 

 higher vertebrates, the gill 

 arches, before and behind 

 this gill slit, namely, the 



first and second, originate -B. Hog. 



C. Musk-ox, 

 middle 



FIG. 214. Stapes of UnQulate Mammals. 

 .Hippopotamus. D. Horse. ^'.Rhinoceros. 



E Tapir. . Elephant. 



FIG 215. Stapes of Carnivorous Mammals. 

 A Seal. B Otter. C'. Bear. D Dog. E Tiger. (Owen.) 



and external ear. The tympanic membrane is formed by the coalescence 

 of the sides of the gill opening at a certain point. Whatever is left of 

 the opening, outside of the point at which this coalescence takes place, 

 becomes the meatus, or external auditory canal. Of the part left inside 



