CETACEA. 139 



pressure." The noise, however, called blowing, shows 

 that the animal forcibly exhausts its lungs of" the pent-up 

 breath, driving the air through the nasal orifices, which, 

 mingled with the water contained in the pouches, rises 

 like spray or dense midst. Fig. 92 represents a section 

 of the head of the porpoise, showing the structure of the 

 nasal apparatus. This apparatus is of little use as an 

 olfactory organ, the sense of smell being very deficient. 

 As respects the organs of sight, we may observe that the 

 eye is very small, and adapted, as in fishes, to the density 

 of the surrounding medium, the cornea being flat, and 

 the crystalline lens globular ; there is no lachrymal gland, 

 but the lids are furnished with certain little glands 

 secreting a fluid adapted for lubricating the eyeball. 

 The external aperture of the ear is minute and capable 

 of being closed at pleasure. Under water the whale 

 hears the smallest sounds, the slightest splash of the 

 oar, but to sounds in the air above, even the report of a 

 cannon, as Scoresby states, it is insensible. Its auditory 

 apparatus, enclosed in a bone (petrous portion of the 

 temple) remarkable for hardness, appreciates only the 

 vibration of water. The sense of taste does not appear 

 to be acute. 



The Cetacea, passing their existence in the wild waste 

 of seas, are capable of remaining submerged for a con- 

 siderable length of time, and the vascular system is modi- 

 fied accordingly, the arteries not only of the limbs, but of 

 the chest and vetebral canal, being singularly plexiform. 

 The discovery of this arrangement is due to the cele- 

 brated W. Hunter, who published an account of it in 

 the Phil. Trans. 1787. These animals, he says, " have 

 a greater proportion of blood than any other known, and 

 there are many arteries apparently intended as reservoirs 

 where a larger quantity seemed to be required in a part, 

 and vascularity could not be the only object. Thus we 

 find that the intercostal arteries divide into a vast number 

 of branches, which run in a serpentine course beneath 

 the pleura (lining membrane of the chest), the ribs, and 

 their muscles," forming a deep maze of intermingled 

 and contorted tubes. " These vessels, everywhere lining 



