X SKIN-GLANDS TONGUE 443 



All the recent Crocodilia possess two pairs of skin-glands, both 

 secreting musk. One pair is situated on the throat, on the inner 

 side of the right and left half of the lower jaw. The opening 

 of the gland, visible from below (see the figure of Crocodilus 

 niloticus, p. 461), is slit-like, and leads into a pocket, which in 

 large specimens is of the size of a walnut ; the bag is filled with 

 a smeary pale brownish substance, a concentrated essence of musk, 

 much prized by natives. The secretion is most active during 

 the rutting time, when the glands are partly everted. My young 

 Crocodiles and Alligators often turned them inside out, like the 

 finger of a glove, when they were taken up and held by force. The 

 other pair lies within the lips of the cloacal slit, and is not visible 

 from the outside. The use of these strongly scented organs, 

 which are possessed by both sexes, is obviously hedonic. The 

 sexes are probably able to follow and find each other, thanks to 

 the streak of scented water left behind each individual. 



The tongue is flat and thick, attached by its whole under- 

 surface, so that it can be elevated but not protruded. It fills the 

 whole space between the two halves of the low^er jaw behind 

 their symphysis. The dorsal surface shows numerous irregular 

 polygonal fields, in the middle of most of which opens the duct of 

 a large mucous gland. Tactile and gustatory corpuscles are 

 scattered over the surface in the shape of tiny wartlike elevations. 

 The hinder margin of the tongue is raised into a transverse fold, 

 which, by meeting a similar fold from the palate, the velum 

 palatinum, can shut off the mouth completely from the deep and 

 wide cavity of the throat, which leads of course into the gullet. 

 Dorsally the choanae open into this cavity ; and since the narial 

 passages are transformed into long tubes, completely surrounded 

 by bone, Crocodiles can lie submerged in the water, with only the 

 nostrils exposed and with the mouth open, and breathe without 

 water entering the windpipe. The opening of the latter, the 

 glottis, is a longitudinal slit, protected by the laryngeal cartilages, 

 opened and closed l)y muscles. There is also a pair of membranous 

 folds within the glottis, which serve as vocal cords. Ventrally 

 below the larynx lies the cartilaginous, liroad, shield-shaped hyoid; 

 on the sides are attached the short hyoid horns. The trachea is 

 long, consists of about sixty or more complete cartilaginous rings, 

 and divides into two short bronchi, likewise protected by complete 

 rings. The trachea is depressed ; its transverse diameter decreases 



