HEART AND BLOOD. 35 



CHAPTER VI. 



OP THE COURSE BY WHICH THE BLOOD IS CARRIED FROM THE 

 VENA CAVA INTO THE ARTERIES, OR FROM THE RIGHT INTO 

 THE LEFT VENTRICLE OF THE HEART. 



SINCE the intimate connexion of the heart with the lungs, 

 which is apparent in the human subject, has been the probable 

 cause of the errors that have been committed on this point, 

 they plainly do amiss who, pretending to speak of the parts of 

 animals generally, as anatomists for the most part do, confine 

 their researches to the human body alone, and that when it is 

 dead. They obviously act no otherwise than he who, having 

 studied the forms of a single commonwealth, should set about 

 the composition of a general system of polity ; or who, having 

 taken cognizance of the nature of a single field, should imagine 

 that he had mastered the science of agriculture ; or who, upon 

 the ground of one particular proposition, should proceed to draw 

 general conclusions. 



Had anatomists only been as conversant with the dissection of 

 the lower animals as they are with that of the human body, the 

 matters that have hitherto kept them in a perplexity of doubt 

 would, in my opinion, have met them freed from every kind of 

 difficulty. 



And, first, in fishes, in which the heart consists of but a 

 single ventricle, they having no lungs, the thing is sufficiently 

 manifest. Here the sac, which is situated at the base of the heart, 

 and is the part analogous to the auricle in man, plainly throws 

 the blood into the heart, and the heart, in its turn, conspicu- 

 ously transmits it by a pipe or artery, or vessel analogous to an 

 artery; these are facts which are confirmed by simple ocular 

 inspection, as well as by a division of the vessel, when the blood 

 is seen to be projected by each pulsation of the heart. 



The same thing is also not difficult of demonstration in those ani- 

 mals that have either no more, or, as it were, no more than a single 

 ventricle to the heart, such as toads, frogs, serpents, and lizards, 

 which, although they have lungs in a certain sense, as they have 

 a voice, (and I have many observations by me on the admirable 

 structure of the lungs of these animals, and matters appertain- 



