steller's account of the sea cow. 193 



A very strong, double membrane constitutes the j)leura. Inside this, one con- 

 tinuous muscle an inch thick is interposed and covers both sides. 



The urinary bladder, 2 lines thick, was very strong, but not larger than a man's 

 head, and smaller than the bladder of an ox. 



The trachea is composed of long, cartilaginous circles or semicircles, but has an 

 entirely anomalous structure. One continuous piece of cartilage is twisted into a 

 spiral and covered with a strong continuous membrane, both inside and outside. But 

 the spirals of the trachea are not everywhere equal in breadth, but in some places the 

 edge of the upper circle is hollowed out to receive the opposite eminence of the lower 

 circle, and so makes it crooked. And so, by the helj) of this double membrane that 

 encircles the trachea, the spirals are kept from being dislocated, either inside or out- 

 side. Through this mutual intertwining the rings are prevented from being loosened 

 laterally. By this spiral structure the trachea is separated into branches below the 

 glottis and reaches to the bronchi, and is seen to be such in the very substance of the 

 lungs; it is so constructed for no other reason, perhaps, than that by the continuity 

 of these spirals the huge mass of lungs may be more easily lifted u]) in breathing; for 

 neither muscles nor anything else give so much help to the motion of lungs, which 

 are situated in the back. 



The glottis is like that of an ox, but is closed by the epiglottis much more closely 

 and firmly than is the case in the laud quadrupeds, so the epiglottis is in proportion 

 much thicker. The diameter of the trachea below the glottis is 4.2 inches. 



The thyroid gland is very large, and when cut it poured out a large quantity of 

 liquid of double consistency and color: that which came from tlie larger exterior 

 glands when cut was of the color of milk, but thicker than sheeij's milk, and sweet 

 to the taste; that which came from the middle portion of the gland or receptacle for 

 the gland was contained in a membranous sac of its own; it was glutinous and had 

 the consistency of meal poultice; it was somewhat sweet, with a very slight taste of 

 bitter, and was yellowish- white in color. It occurred to me only in the last animal 

 that I opened to make a closer inspection of this gland. I am very sorry that I did 

 not think of it sooner, and take the pains to have the trachea, with the gullet, heart, 

 and the rest of the viscera taken out entire. But it was not possible without the 

 help of many men to do so with an animal so huge. If I had been in a position to do 

 that, I should have observed whether or not it unloaded this liquid through some tube 

 into a duct of its own, or into the stomach, as Vercellonius thought, or somewhere 

 else. I saw the duct only after it was cut, but whither it led I neither saw nor do I 

 wish to conjecture. 



As to the heart it differs in many respects from the heart of all other animals: (1) 

 In regard to situation, the apex of the heart stands in a line oblique to the sternum, 

 the base in a line oblique to the back. (2) As to connection, the heart does not rest 

 against the mediastinum, but is detached on every side and has no mediastinum at 

 all. (3) It has a pericardium (but this does not envelope the heart closelj^) and 

 a sac; but it forms rather a species of cavity in the thorax and lines the thorax. 

 Toward the back and the base of the heart the pericardium is nearer to the heart than 

 it is anywhere else. When the animal is fieeding, the heart itself, with the pericar- 

 dium, hangs not quite perpendicularly but somewhat obliquely from back to sternum; 

 and so there the i^ericardium takes the place of a mediastinum. Lower down toward 

 the abdomen the pericardium is fastened to the inner wall of the diaphragm, and with 

 5947_px 3 13 



