12 Observations on the Natural History 



vations, say the authors, not only illustrate certain facts regard- 

 ing the proteus, but may apologise for those learned writers, 

 who, from not having had the opportuntity of dissecting this 

 animal when recently dead, have deviated, in their anatomical 

 descriptions, some little from the truth. 



5. Of the Organs of Circulaticm. 



The heart of the proteus is lodged in that triangular space 

 which is formed by the branchial arches. Its situation and size may 

 be seen in Plate VII. Fig. 1. Its structure is simple, consisting, 

 like that of the frog, of one auricle and one ventricle. In figure, 

 also, it resembles the heart of the frog, but is somewhat smaller 

 in proportion. Its auricle is placed forward, and over the ven- 

 tricle ; is slightly toothed on its margins ; and to the eye seems 

 as large as the ventricle itself 



From the base of the heart on the right side, springs a very 

 short canal, which proceeds straightforward ; but before it gets 

 beyond the auricle, by which it is covered, it expands into a 

 bulbous form. This short canal, the only one that goes out from 

 the heart, is of a soft fibrous texture, similar to that of the heart 

 itself. The bulbous part, on the contrary, possesses great 

 strength, and is opake and tendinous. Hence it is, that whe- 

 ther it be empty or full of blood, it exhibits always a whitish 

 pearly colour, different entirely from the other parts of the ves- 

 sels, which, when full of blood, appear of a reddish or russet 

 hue. 

 From this bulb proceed two large arteries, which, almost imme- 

 diately on quitting it, separate from each other, and are direct- 

 ed, on either side, towards the branchial arches. These two ar- 

 teries, for greater clearness and convenience of description, are 

 called the two 'primary trunks ; but the authors will speak 

 only of one, since what is said of one will apply equally to the 

 other. 



The primary trunk, then, of the right side, very soon after quit- 

 ting its fellow, gives off a branch which runs under the first arch 

 through its whole length, where it sends off two arteries, one to 

 the first gill, and the other to the muscles of the os hyoides ; af- 

 terwards, abandoning the arch, and turning upward and inward, 

 it goes to the roof of the occiput. This first branch from the 



