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, which are modified folds of the 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 are situated almost solely at 
the upper end of the trachea or windpipe. In the voiceless 
whales the vocal cords are not developed. The male 
gorilla, which 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 third 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 hours" (Darwin). They 
-apparently howl, 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 the attacks of other species by odors. The 
scent-bags or odoriferous 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 they may be developed in the side of the 
face, as in the male elephant, as well as sheep and goats. 
The odor is either of musk or some form of it. The shrew- 
mice, by reason of their odoriferous glands, are disliked 
and consequently not hunted by birds. Universal defer- 
ence is paid to the skunk; few dogs, and only those which 
«3,re inexi^erienced or peculiarly gifted^ attacking them. 
