180 M. F. Cuvier De VHistoirc 



species would only increase its popularity. This is true of the other 

 orders of the animal series. The fossil elk, the great mammoth, the 

 extinct rhinoceros, the cave-bear, and many others which might be 

 mentioned, are not the least interesting species of their respective gene- 

 ra, and are most attractive objects of natural history as beings of a by- 

 gone age, not one of which could be distinguished except by a most 

 minute comparison with the living species. And surely, therefore, 

 in a work like the present, which is altogether of a scientific cast, 

 it seems a pity that they should be wholly neglected ; the more so, 

 as the science of geology must always turn to the zoologist for all 

 the information it desiderates concerning this interesting department 

 of its fascinating inquiries. 



We now proceed to lay before our readers whatever appears most 

 new and interesting in the work before us. 



The preliminary discourse, extending to fifty pages, is composed 

 of a general survey of the order, and dwells more especially on the 

 peculiarities of their comparative anatomy. Here our author is mi- 

 nute and lucid, describing the internal as well as the external struc- 

 ture. One of the most interesting statements relates to a peculia- 

 rity of the arterial system, which is connected with the function of 

 respiration. It consists in an innumerable congeries, — a vast 

 plexus of great arteries, which, after respiration, is filled with 

 highly purified blood, and which is lodged beneath the pleurae, be- 

 tween the ribs, and on each side of the spine. The vessels forming 

 this plexus rise from the upper intercostals, and they penetrate into 

 the vertebral canal, and even into the cranium, by the occipital fora- 

 men. The plexus is not formed of ramifications which anastomose with 

 each other, for they may in some degree be followed out, and unra- 

 velled as if they were only a single vessel twisted a thousand times 

 upon itself. In addition to their connection with the intercostals, 

 they are also connected with the vertebrals and carotids. They do 

 not appear to communicate directly with any vein. The vena azygos 

 is not situated anteriorly to the spinal cord, but is replaced by a 

 considerable trunk on each side and posteriorly to the cord, which 

 receives the intercostal and lumbar veins, and joins the superior ve- 

 na cava. It is conceived that this singular structure is connected 

 with the occasional long- continued suspension of respiration in the 

 Cetacea ; extending to the long period of an hour, and sometimes 

 even more. These vessels, it will be seen, become a reservoir of 

 highly arterialized blood, which entering gradually into the circula- 

 tion will, for a long period, maintain life.* 



* See p. xvii. 90. 



