i84 



A 



DESCRIPTION OF THE HEART, 

 VESSELS AND CIRCULATION OF THE BLOOD 



IN FISHES, 



BY ALEXANDER MONRO. 



I. li 



CHAPTER I. 



n ijll the fishes* I have difTedled, there is but one heart, 

 confiding of onc auricle and one ventriclc, and, fiom thc 

 latter, one artery is fent out, which is en tirely fpent on thc 

 gills. From the gills, therefore the returning blood paiTes to 

 all the other parts of the body, without the intervention ofa 

 fecond heart, as in man (a), 



2. So far is generally known! but the whole courfe of 

 the blood has not been traced with fufhcient accuracy; fo that 

 feveral curious and hiterrefling circuai/lances have efcaped 

 notice. 



3-1 



(/i) To he iiiore reacUIy underftood, I fhall generally apply the 

 teriiis fore, Lack, iipper, nmier, inner , outer^ m the famc 

 manner as is done in fpeaking of the hiiiDan body: or I fhall 

 fuppofe the fish to be placed ere6t with it9 hcad uppernioft. 

 But in defcribing the ear and other parts, ofthehead itfclf, 

 I f hall fuppofc the fish in its natural fituation, as the brain 

 and organs of the fcnfes have not the fame dire6tion as in inan, 

 "with refpcdl to the trunk of the body. 



If iupgs, as well as gills, are found in the Pctromyzon 

 and Diodon of Linnaeus, it is probable there niay bc two ven* 

 tricles in their heart. 



rCor uniauritum et uniloculare in Petromyzo marino egoet 

 Bloch, in Diodonte Mola vero ]nnns Plancus obfervaverunt^ 

 Vide Qonnn Bonon Tom 2, P 2. pag 279 ) 

 / In the Sepia, which has bcen generally confidcred as a fish, 

 but which is with more propriety reckoned , a worm by Lin- 

 fiaeus, I have, many years ago, discovcrcd three hearts. 



