DR. J. MURIE ON THE FOEM AND STRUCTUIIB OF THE MANATEE. 175 



On section the liver exhibits a fine glandular structure, and not a coarse lobular 

 substance as in some Ruminants. The interior of the gall-bladder is smooth. 



VI. Organs of Circulation. 



1. The Heart. 

 The following tabular arrangement expresses in inches and tenths the several dimen- 

 sions of the heart of the female Manatee when contracted as ordinarily after death, in 

 this case, however, having been very slightly preserved in spirit : — 



Right auricle. Left auricle. 



Extreme length 1-3 1-6 



Extreme breadth IT 1"5 



Right ventricle. Left ventricle. 



Extreme length, anteriorly 2'4 2"8 



Extreme length, posteriorly 2-0 2"8 



Extreme breadth at base, anteriorly .... 2-7 2'3 



Extreme breadth at base, posteriorly . . . . 2'4 2*5 



Extreme breadth at apex I'l 1-5 



Extreme thickness of walls I'O 1'5 



This organ has been so repeatedly described that I can add nothing material to the 

 statements of previous observers, and agree with them as to its cleft nature. 



2. Blood-vessels and Lymphatic Glands. 



The arterial distribution of the American Manatee has been so lucidly explained in 

 the masterly compendium on the vascular system by Professor Hermann Stannius', that, 

 were it illustrated, I should be content to leave the subject untouched. But the 

 remarkable character of the vessels, splitting up, as they do, in certain parts into multi- 

 farious plexuses and rete mirabile, is a sulBcient reason why they should be figured and 

 further commented on. 



According to the above author, and as my dissection (fig. 30, PI. XXIV.) demon- 

 strates, a short, wide, innominate trunk springs from the arch of the aorta, and di^ides 

 into a right subclavian and common carotid. From the summit of the arch the left 

 common carotid is derived ; and, lastly, further beyond is the left subclavian. As regards 

 the carotid and branches, he states only that the common carotids have tolerably long 

 stems, which, at first glance, appear to simulate division into an external and internal 

 carotid, although this does not truly take place. The first main branch of the carotid 

 proceeds inwards, and supplies the larynx, the hyoid apparatus, and the tongue. 



What I have found obtain is as follows : — The stem of the fair-sized common carotid 

 is branchless until about opposite the deep hollow in front of the shoulder or supra- 

 ' Op. cit. p. 31 et seq., also Von Baer, Mem. d. I'Acad. St. Petersb. 1835, torn. ii. p. 199. 



VOL. VIII. — PART III. September, 1872. 2d 



