Gi 
analogy, is wonderfully manifested. “ In man, and 
the more complicated animals of the vertebral divi- 
sion, circulation is a function of the first importance. 
The blood, proceeding from the left ventricle of the 
heart, spreads itself by the arteries through the 
whole body, takes the capillary system in its way, 
passes into the veins; returns to the heart, enters 
into the right auricle of that organ, then into the 
corresponding ventricle; which in its turn sends it 
into the pulmonary artery, to be distributed into the 
lungs; from which it issues by the pulmonary veins, 
to repair to the left auricle and ventricle, and pro- 
ceed from thence in its round anew. In this course, 
the blood evidently describes a double circle; one 
in the lungs, the other in the entire body. This is 
not the case with the reptiles. The heart in these 
animals sends into the lungs, at each contraction, 
but a portion of the blood: therefore the pulmonary 
circulation is but a fraction of the general circula- 
tion. The quantity of their blood, e. g. in the sau- 
rians, is very small in comparison with that of mam- 
mifera and of birds".” In zoophytes, intestinal 
worms, &c. the circulatory system is not distinguish- 
able from ramifications of the intestinal canal. In 
the leech and earthworm the vascular system is 
more developed. In crustacea, generally, the heart 
is an elongated aorta stretched along the back, as in 
vermes. Yet in crabs are traces of a rounded heart. 
Amongst insects there appear to be differences of 
u Cuvier’s Animal Kingdom, translated by Griffith, part xxv. 
pa TSE: 
