HEARING. 619 
that terrier dogs also have a very acute sense of hearing, and 
they also kill rats, ete. But, unless it be denied that the im- 
provement from use and the reverse can be inherited, this fac- 
tor must also be taken into the account. 
There seem to be great differences between hearing as it 
exists in man and in lower forms. Birds, and at least some 
horses, possibly some cats and dogs, like music, and give evi- 
dence of the possession of a sense of rhythm, as evidenced by 
the conduct of the steed of the soldier. On the other hand, 
some dogs seem to greatly dislike music. Certain animals that 
Aa, pT ranaverse eeetion. through head of total epeep a Femion of aisd-praln, to illus- 
vertical penicioular aul oe, canal at einhicn ; RY, feccaun Westibul) GC; auditory 
ganglion ; G’, terminal portion of auditory nerve. . 
appear to be devoid of true hearing, as spiders, are neverthe- 
less sénsitive to aérial vibrations; whether by some special un- 
discovered organ or through the general cutaneous or other kind 
of sensibility is unknown. It also seems to be more than prob- 
able that some groups of insects can hear sounds quite inaudible 
to us, though by what organs is in great measure unknown. 
The so-called musical ear differs from the non-musical in 
the ability to discriminate differences in pitch rather than in 
quality ; in.fact, that one defective in the former power may 
possess the latter in a high degree is a fact that has been some- 
what lost sight of, both theoretically and practically. It does 
not at all follow that one with little capacity for tune may not 
