76 MOTION OF THE 



mussels, sponges, and the whole genus of zoophytes or plant- 

 animals have no heart ; for the whole body is used as a heart, or 

 the whole animal is a heart. In a great number of animals, 

 almost the whole tribe of insects, we cannot see distinctly by 

 reason of the smallness of the body ; still in bees, flies, hornets, 

 and the like, we can perceive something pulsating with the help 

 of a magnifying glass ; in pediculi, also, the same thing may 

 be seen, and as the body is transparent, the passage of the food 

 through the intestines, like a black spot or stain, may be per- 

 ceived by the aid of the same magnifying glass. 



In some of the bloodless 1 and colder animals, further, as in 

 snails, whelks, shrimps, and shell-fish, there is a part which 

 pulsates a kind of vesicle or auricle without a heart slowly 

 indeed, and not to be perceived save in the warmer season 

 of the year. In these creatures this part is so contrived that 

 it shall pulsate, as there is here a necessity for some impulse to 

 distribute the nutritive fluid, by reason of the variety of organic 

 parts, or of the density of the substance ; but the pulsations 

 occur unfrequently, and sometimes in consequence of the cold 

 not at all, an arrangement the best adapted to them as being 

 of a doubtful nature, so that sometimes they appear to live, 

 sometimes to die; sometimes they show the vitality of an animal, 

 sometimes of a vegetable. This seems also to be the case with 

 the insects which conceal themselves in winter, and lie, as it 

 were, defunct, or merely manifesting a kind of vegetative exist- 

 ence. But whether the same thing happens in the case of 

 certain animals that have red blood, such as frogs, tortoises, 

 serpents, swallows, may be made a question without any kind 

 of impropriety. 



In all the larger and warmer, because [red-] blooded animals, 

 there was need of an impeller of the nutritive fluid, and that 

 perchance possessing a considerable amount of power. In fishes, 

 serpents, lizards, tortoises, frogs, and others of the same kind 

 there is a heart present, furnished with both an auricle and a 

 ventricle, whence it is perfectly true, as Aristotle has observed, 2 

 that no [red-] blooded animal is without a heart, by the im- 

 pelling power of which the nutritive fluid is forced, both with 

 greater vigour and rapidity to a greater distance; it is not 



[' i. e. Not having red blood. ED.] 2 De Part. Animal, lib. iii. 



