KNOX ON THE CETACEA. 73 



distinct as in man. In the rectum the folds of the mucous mem- 

 brane were transverse. 



Organs of Hespiration. — The external nostrils were double ; and 

 the cavities of the nostrils provided with the remarkable carti- 

 lages and muscular apparatus I discovered and described in the 

 anatomy of the Grreat Eorqual. In this specimen they were about 

 4 inches in length, but of as many feet in the large Eorqual. The 

 mode of breathing in the Eorquals does not differ much from that 

 in man, with the exception of the apparatus of the protruding 

 cartilages, which in man are rudimentary. 



The Olfactory Nerves were quite as large as in other mammals ; 

 and in this respect the Balaena "Whales are quite unlike the Dol- 

 phins *. 



The trachea communicated, near its upper part, with a sac or 

 pouch; the lungs were each composed of a single lobe. The 

 rings of the trachea were mostly deficient anteriorly. In the 

 heart the foetal arrangements had wholly disappeared. The dura 

 mater seemed divisible into three layers, the external being vas- 

 cular. A remarkable vascular substance connected with this layer 

 covers the back part of the brain and cerebellum, extending into 

 the spinal canal, and even into the chest. At the base of the 

 brain the vascular plexus was about 2 inches in thickness. It is, 

 as is well known, a sort of erectile tissue, of whose functions 

 we are wholly ignorant. It is not confined to this course, but 

 extends to the neck, and, passing through the foramina inter- 

 vertebralia, fills the intercostal spaces exterior to the pleura. 



There was evidently a canal in the centre of the spinal marrow. 

 Wherever the nerves of the lungs and stomach were traced, they 

 terminated in loops. "We did not observe in the Grreat Eorqual 

 any tracheal pouch like that in the smaller ; but it may have 

 escaped notice: if absent in the Grreat Eorqual, it would be 

 another proof of the distinctness of the species. 



The doubts raised by M. St. Hilaire, as to the Whale being a 

 mammal in the true sense of the term, were set aside long ago by 

 an appeal to facts. The young of the Whale tribe suckle like 

 the young of all mammals ; nevertheless I showed, in 1834, that 



* In his paper " On the Structure of Whales " (PhH. Trans. 1787), Hunter 

 remarks that the organ of smell " is peculiar to the large and small Whalebone 

 Whales." He further remarks, that, " in those that have olfactory nerves, the 

 lateral ventricles are not continued into tliem as in many quadrupeds ;" and 

 he notices " the want of the olfactory nerves in the genus of the Porpoise." — 

 ' Anim. Economy,' Pahner's edit. pp. 372, 373, 376. 



