REGARDED AS A MASS. 
11 
of sides. Yet that symmetry which depends upon the cor¬ 
relation of the sides, is externally preserved throughout the 
whole trunk; and is the more remarkable in the lower parts of 
it, as the integuments are soft; and the shape, consequent¬ 
ly, is not, as the thorax is by its ribs, reduced by natural 
stays. It is evident, therefore, that the external proportion 
does not arise from any equality in the shape or pressure 
of the internal contents. What is it indeed but a correc¬ 
tion of inequalities? an adjustment, by mutual compensa¬ 
tion, of anomalous forms into a regular congeries? the ef¬ 
fect, in a word, of artful, and, if we might be permitted so 
to speak, of studied collocation? 
3. Similar also to this, is the third observation; that an 
internal inequality in the feeding vessels is so managed, 
as to produce no inequality in parts which were intended 
to correspond. The right arm answers accurately to the 
left, both in size and shape; but the arterial branches, 
which supply the two arms, do not go off from their trunk, 
in a pair, in the same manner, at the same place, or at 
the same angle. Under which want of similitude, it is 
very difficult to conceive how the same quantity of blood 
should be pushed through each artery: yet the result is 
right; the two limbs, which are nourished by them, per¬ 
ceive no difference of supply, no effects of excess or de¬ 
ficiency. 
Concerning the difference of manner, in which the sub¬ 
clavian and carotid arteries, upon the different sides of 
the body, separate themselves from the aorta, Cheselden 
seems to have thought, that the advantage which the left 
gain by going off at a much more acute angle than the 
right, is made up to the right by their going off together 
in one branch.* It is very possible that this may be the 
compensating contrivance; and if it be so, how curious, 
how hydrostatical ? 
II. Another perfection of the animal mass is package . 
[PI. XXII. fig. 1.] I know nothing which is so surprising. 
Examine the contents of the trunk of any large animal. 
Take notice how soft, how tender, how intricate they are; 
how constantly in action, how necessary to life! Reflect 
upon the danger of any injury to their substance, any de¬ 
rangement of their position, any obstruction to their office. 
Observe the heart pumping at the centre, at the rate of 
eighty strokes in a minute: one set of pipes carrying the 
stream away from it, another set bringing, in its course, the 
* Ches. Anat. p. 184. ed. 7. 
