CETACEA. 



CETACEA. 



890 



organs deviates in a marked degree from the ordinary Cetacea, in the 

 presence of a well-developed gall-bladder, an organ which Daubentou 

 also found in the Manatee. But the presence of the gall-bladder is not, 

 the Professor observes, constant in the Herbivorous Cetacea ; for in the 

 Northern Manatee, according to Steller, it is wanting, and its absence 

 seems to be compensated by the enormous width of the ductus com- 

 niuiiis choledochus, which would admit the five fingers united. The | 

 secretion of the pancreas was carried by from twenty to thirty ducts, each 

 about two lines in diameter, to a very wide common excretory canal, 

 which terminates below, but on the same prominence with the cystic 

 duct, at a much greater relative distance from the pylorus than in 

 the true Cetacea. In one of the Dugongs dissected by Professor Owen 

 were two small accessory spleens in addition to the larger rounded 

 one, but in the other specimens the last alone was present. (' Zool. 

 Proc.,' 1838.) 



Zoophagous Cetaceans. The teeth of the Dolphins are generally i 

 simple and conical or compressed. They are present in both jaws ; 

 their number varies, and they not unfrequently lie hid in the gums in 

 a rudimentary state. Those of the Cachalots are simple, of a long \ 

 ovoid recurved shape, and placed in the lower jaw only. The Mysti- 

 cetes, or Whalebone Whales, are without true teeth ; in lieu of which, 

 transverse horny plates of baleen, or whalebone, as it is commonly 

 termed, grow from the palate. These plates on their internal edges 

 are fringed with loose beards, and among these the small marine 

 animals which form their food are entangled as in the meshes of 

 a net. 



The stomachs of the Zoophagous Cetaceans are very complicated : 

 the number of these in various species, and in different individuals of 

 the same species, has been variously given by different authors. 

 Some have stated the number in the common Dolphin and Porpesse 

 at three, others at four, others at five, others at six. F. Cuvier con- 

 siders it as certain that these numerical differences proceed simply from 

 the manner in which the organ is viewed. Professor Owen was unable 

 to distinguish more than four compartments in the stomach of the 

 Porpesse. In general the spouting whales have no caecum ; but a 

 trace of it has been found in the Platanist, and it actually exists in 

 the Piked and Whalebone Whales. 



John Hunter pointed out the considerable degree of uniformity 

 present in the liver of this tribe, observing that in shape it resembles 

 that of man, but that it is not so thick at the base nor so sharp at 

 the lower edge, and probably not so firm in the texture. The right 

 lobe is the largest and thickest. There is no gall-bladder. The same 

 distinguished comparative anatomist describes the pancreas as a very 

 long flat body, having its left end attached to the right side of the 

 first cavity of the stomach : it passes, he adds, across the spine at the 

 foot of the mesentery, and near to the pylorus joins the hollow curve 

 of the duodenum, along which it is continued and adheres to the 

 intestine, its duct entering that of the liver near the termination of 

 the gut In the Piked Whale the spleen is single and small ; in the 

 Porpesse it is subdivided into several distinct portions. 



There is an interesting, series of preparations illustrative of the 

 anatomy of the Cetacea in the museum of the College of Surgeons, 

 and well deserving the attention of the student of comparative ana- 

 tomy. One of these preparations, No. 323, is a perpendicular section 

 of several plates of whalebone, with the intermediate substance and 

 vascular nidus, from the upper jaw of a young specimen of the Great 

 Whale (Balatna myiticttiu, Linn.). The disposition and relative pro- 

 portions of the plates of whalebone are here shown ; from which dispo- 

 sition it results, that only the fringed extremity of the whalebone 

 plates are visible from the inside of the mouth of the whale ; the 

 whole concavity of the palate appearing to be beset with coarse rigid 

 hairs or bristles, which explains the passage in Aristotle (' Hist A uiin.' 

 iii. 12), who, speaking of the Great Whale (' HUOTI'/OJTOJ, or, aa Bekker 

 reads it, 6 /tvs rb (t^ros), says, " The Mysticete has no teeth in its mouth, 

 but hairs like hog's bristles." 



Circulating System. Phytophagous Cetaceans. The three Dugongs 

 dissected by Professor Owen presented the same remarkable extent 

 of separation of the two ventricles of the heart described by Sir 

 Everard Home and Sir Stamford Raffles in the individuals examined 

 by them, and observed by Riippell in the Dugong of the Red Sea 

 ( JMicore Tabernaculi). Daubenton appears to be the first who noticed 

 this condition of the heart, in his dissection of the foetus of the Mana- 

 tee. Steller also described it in the genus which bears his name ; but 

 in that animal the apical cleft of the heart extended upwards only 

 one-third of the way towards the base, whereas in the Dugong it 

 reaches half-way towards the base. 



Professor Owen found the foramen ovale completely closed, and the 

 ductus arteriosus reduced to a thick ligamentous cord, permeable 

 for a short distance by an eye-probe from the aorta, where a crescentic 

 lit still represented the original communication. He states that in 

 the smoothness and evenness of their exterior and their general form 

 the auricles of the Dugong resemble those of the Turtle (Chelone), 

 and that the appendix can hardly be said to exist in either. The 

 right auricle is larger than the left. The primary branches from the 

 arches of the aorta correspond in each specimen with Sir Everard 

 Home's figure and description. There was only one superior cava, 

 not two, as in the Elephant ; and the pulmonary veins terminated in 

 the left auricle by a common trunk an inch in length. 



As no mention had been made in the anatomical descriptions of the 

 Herbivorous Cetaceans by Daubentou, Steller, Cuvier, Raffles, aud 

 Home, respecting the existence or otherwise of the extraordinary 

 intercostal and intervertebral arterial plexuses present in the true 

 Cetacea, Professor Owen carefully followed out this part of the dis- 

 section, but could detect no trace of this very striking modification. 

 Here again, he observes, in enunciating a general anatomical propo- 

 sition regarding Cuvier's Cetacea, the Herbivorous species must be 

 exceptionally cited apart. 



Zoophagous Cetaceans. Professor Owen remarks that the Carni- 

 vorous Cetaceans do not participate in the structure of the heart above 

 described with the Herbivorous section. 



The following is John Hunter's description of the heart of the 

 Whale : 



" The heart is inclosed in its pericardium, which is attached by a 

 broad surface to the diaphragm, as in the human body. It is com- 

 posed of four cavities two auricles and two ventricles : it is more 

 flat than iu the quadruped, and adapted to the shape of the chest. 

 The auricles have more fasciculi, and then pass more across the cavity 

 from side to side, than in many other animals ; besides being veiy 

 muscular they are very elastic, for being stretched they contract again 

 very considerably. There is nothing uncommon or particular in the 

 structure of the ventricles, in the valves of the ventricles, or in that 

 of the arteries. The general structure of the arteries resembles that 

 of other animals ; and where parts are nearly similar, the distribution 

 is likewise similar. The aorta forms its usual curve, and sends off 

 the carotid and subclaViau arteries. The veins, I believe, have nothing 

 particular in their structure, excepting in parts requiring a peculiarity, 

 as in the folds of the skin on the breast in the Piked Whale, where 

 their elasticity was to be increased." 



This assertion respecting the veins is not stated very positively, 

 and we shall presently see that there is a peculiarity in their 

 structure. 



The same great physiologist well observes, that in our examination 

 of particular parts, the size of which is generally regulated by that 

 of the whole animal, if we have only been accustomed to see them in 

 those which are small or middle sized, we behold them with astonish- 

 ment in animals so far exceeding the common bulk as the Wh;iK-. 

 " Thus," says Hunter, " the heart and aorta of the Spermaceti Whale 

 appeared prodigious, being too large to be contained in a wide tub, 

 the aorta measuring a foot in diameter. When we consider these as 

 applied to the circulation, and figure to ourselves that probably 10 or 

 15 gallons of blood are thrown out at one stroke, r nd moved with an 

 immense velocity through a tube of a foot diameter, the whole iden 

 fills the mind with wonder." 



But the most remarkable modification of the arterial system in the 

 Whales remains to be noticed. This consists iu an almost infinite 

 circumvolution of arteries, forming a plexus of vessels filled with 

 oxygenated blood, situated under the pleura and between the ribs, on 

 each side of the spine. This intercostal plexus, or rete mirabile, is 

 the apparatus which enables the whale to remain xmder water for 

 more than an hour. 



M. Breschet read a paper to the French Academy of Sciences in 

 1834, which bears the following title : ' Histoire Anatomique et Phy- 

 siologique d'un Organe de Nature vasculaire decomert dans les Ce'tace's, 

 etc.' M. Breschet has however no claims to the discovery of this 

 organ. It was indicated and described long ago by Tyson in his 

 ' Anatomy of a Porpesse,' but he was not aware of the use of it, and 

 considered it as a glandulous body. Hunter was the first who deter- 

 mined its exact nature, and showed that it was a reservoir of arterial 

 or aerated blood. 



After noticing the general structure of the arteries as above men- 

 tioned, and stating that the aorta forms its usual curve, sending off the 

 carotid and subclavian arteries, Hunter proceeds as follows : 



" Annuals of this tribe, as has been observed, have a greater pro- 

 portion of blood than any other known, and there are many arteries 

 apparently intended as reservoirs, where a largo quantity of arterial 

 blood seemed to be required in a part, and vascularity could not bo 

 the only object. Thus we find that the intercostal arteries divide into 

 a vast number of branches, which run in a serpentine course between 

 the pleura, ribs, and their muscles, making a thick substance, some- 

 what similar to the spermatic artery in the Bull. These vessels, 

 everywhere lining the sides of the thorax, pass in between the ribs 

 near their articulation, and also behind the ligauieutous attachment 

 of the ribs, and anastomose with each other. The medulla spinalis 

 is surrounded with a net-work of arteries in the same manner, more 

 especially where it comes out from the brain, where a thick substance 

 is formed by their ramifications and convolutions ; and these vessels 

 most probably anastomose with those of the thorax. The subclavian 

 artery in the Piked Whale, before it passes over the first rib, sends 

 down into the chest arteries which assist in forming the plexus on the 

 inside of the ribs. I am not certain but the internal mammary arteries 

 contribute to form the anterior part of this plexus. The motion 01 

 the blood in such cases must be very slow ; the use of which we do 

 not readily see. The descending aorta sends off the intercostals, 

 which are very large, and gives branches to this plexus ; and when 

 it has reached the abdomen it sends off, as in the quadruped, the 

 different branches to the viscera and the lumbar arteries, which are 



