240 ZOOLOGY. 



of the uppermost ring of the windpipe, called the cricoid 

 cartilage, to the anterior and dorsal edges of which two 

 arytenoid cartilages are attached, while a V-shaped thyroid 

 cartilage, open behind, is attached to its side. The vocal 

 cords, whicli are modified folds of tlie mucous membrane 

 lining the windpipe, are stretched between the arytenoid 

 and thyroid cartilages, the slit between them being called 

 the glottis, which is covered by the epiglottis. Thus, in 

 mammals the organs of voice aie situated almost solely at 

 the upper end of the tracliea or windpipe. In the voiceless 

 whales the vocal cords are not developed. The male 

 gorilla, whicli has an exceedingly loud voice, as well as the 

 adult male orang and the gibbon, is provided with a laryn- 

 geal sac. In the howling monkey of Brazil, the hyoid 

 apparatus and larynx are remarkably modified, the body 

 of the former being changed into a large bony drum or 

 air-sac communicating with the larynx. The vocal organs 

 are a tliird larger in the males than in the females. "The 

 males begin the dreadful concert, in which the females, 

 with their less powerful voices, sometimes join, and which 

 is often continued during many houi's" (Darwin). They 

 apparently liowl, as birds sing, for the simple pleasure of 

 the thing. Apparently, the most musical mammal, man 

 excepted, is a gibbon, which can sing "a complete and 

 correct octave of musical notes." 



Animals are mutually attracted or are individually pro- 

 tected from tlie attacks of other species by odors. The 

 scent-bags or odorifei'ous glands secreting a fluid differing 

 in consistency in different animals, are situated near the 

 base of the tail, as in the skunk, pole-cat, musk-deer, civet- 

 cat and allies, or tliey may be develo])ed in the side of the 

 face, as in the male elepliant, as well as sheep and goats. 

 The odor is eitl}er of musk or some form of it. Tlie shrew- 

 mice, by reason of tlieir odoriferous glands, are disliked 

 and consequently not hunted by birds. Universal defer- 

 ence is paid to the skunk; few dogs, and only those which 

 are inexperienced or peculiarly gifted, attacking them. 



