and run. Infants, therefore, resemble dwarfs in the beginning, and they creep about like quadrupeds, attempting progres- sive motion with the assistance of all their extremities ; but they cannot stand erect until the length of the leg and thigh together exceeds the length of the rest of the body. And so it happens, that when they first attempt to walk, they move with the body prone, like the quadruped, and can scarcely rise so erect as the common dunghill fowl.
And so it happens that among adult men the long-legged they who have longer legs, and especially longer thighs are bet- ter walkers, runners, and leapers than square-built, compact men.
In this second process many actions of the formative faculty are observed following each other in regular order, (in the same way as we see one wheel moving another in automata, and other pieces of mechanism,) and all arising from the same mu- caginous and similar matter. Not indeed in the manner that some natural philosophers would have it when they say, "that like is carried to its like." We are rather to maintain that parts are moved, not changing their places^ but remaining and undergoing change in hardness, softness^ colour, &c., whence the diversities between similar parts those things appearing in act which were before in power. 1 The extremities, spine, and rest of the body, namely, are formed, grow, and acquire outline and complexion toge- ther; the extremities, comprising bones, muscles, tendons, and cartilages, all of which on their first appearance were simi- lar and homogeneous, become distinguished in their progress, and, connected together, compose organs, by whose mutual continuity the whole body is constituted. In like manner, the membrane growing around the head, the brain is com- posed, and the lustrous eyes receive their polish out of a per- fectly limpid fluid.
That is to say, nature sustains and augments the several parts by the same nourishment with which she fashioned them at first, and not, as many opine, with any diversity of aliment and particles similar to each particular structure. As she is increasing the mucaginous mass or maggot, like a potter she first divides her material, and then indicates the head and trunk
De Gen. Anim. lib. ii, cap. 4.
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