THE SENSE-ORGANS 



489 



serve to hold and protect the others. These spots, which thus 

 show a higher degree of cellular differentiation, are the seat 

 Df the auditory sense, and appear from their greater thickness 



Mac. 



Wacsac 



FIG. 133. Ear labyrinths of various Vertebrates. [After RETZIUS.] 



(a) Cyclostome; Myxine glutinosa (hag fish), (b) Selachian; Chimaera monstrosa, 

 (c) Teleost; Anarrhichas lupus (wolf-fish), (d) Amphibian; Rana esculenta (frog), 

 (e) Bird; Bubo ignavus (horned owl), (f) Mammal; Sus scrofa domestica (pig). 

 aa, ampulla anterior; ae, ampulla extcrna; ap, ampulla posterior; e, ductus 

 endolymphaticus: fac, facial nerve; mac, macula communis; mac. utr, macula 

 utriculi; mac. sac, macula sacculi; , macula neglecta; pap. lag, papilla lagenae; 

 pap. bos, papilla basilaris. 



as white patches in the otherwise transparent wall. They are 

 further indicated by their association with the nerve. 



The largest occurring number of such auditory areas is eight, 

 although all do not occur simultaneously. Of these the three 

 which are associated with the semicircular canals are some- 



