
-DESCRIPTION. OF THE HEART, 
VESSELS AND CIRCULATION OF THE BLOOD. 
IN. FISHES, 
BY ALEXANDER. MONRO. 


CHAPTER I. : 
f. Y. all the fishes, I have diffected, there is but one heart, - 
confifng of one auricle and one ventricle, and,' from the 
latter, one artery is fent out, which is en ticely fpent on the 
gill; From the gills, ihdreire the returning blood paffes to 
all the other parts of the body, without the intervention of a 
fecond heart, as in man (a). 3 
2. So far is generally known! but the whole courfe of. 
the blood has not been traced with (ufficient accuracy ; fo that ^ 
feverel curious and iaterrefting circumftances have e[caped 
notice. j 
3.1 
(4) To he more readily underftood, I fhall generally apply the 
terms fore, back , upper , under, inner, Ooufev, in the fame 
manner as is done in fpeaking of the human body: .or I fhall 
fuppofe the fish to be placed ere& with its head uppermoft, 
But in defcribing the ear and ether parts, ofthe head itfel£, 
I fhall fuppofe T fish in its natural fituation, as the bran 
and organs of the fenfes have not the fame direction as in man, 
with refpect to the trunk of the body, 
If lungs, as well as gills, are found. in the Petromyzon 
and Diodon of Linnaeus, itis probable there may be two ven- 
tricles in their heart. 
( Cor uniauritum et uniloculare in Petromyzo marino ego et 
Blocb, in Diodonte Mola vero /azmus Plancus obíervaverunt, 
Vide CE Bonon 'Tom 2. P. 2. pag. 279). 
In the Sepia, which has been generally confidered as a fish, 
but which is with more propriety reckoned, a wort by D 
naeus, I have, many years ago, discovered three hearts, 



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