Page:The third Huxley lecture.pdf/37

33 was allowed to remain, whether a little caudal segment or a small anterior part, the arteries resumed, after temporary dilatation, their ordinary and varying dimensions.

It was thus shown that the cerebro-spinal axis is the centre that presides over the contractions of the arteries of the foot, and that the function is exercised by the entire posterior half of the cord

The very transient effect of section of the sciatic proved that, as is the case with the pigmentary functions, one nerve can take the place of others in the duty. And I found that even after division of all the soft parts of the thigh except the main artery and vein, the vessels of the webs soon recovered their contractile power; showing that the control of the cord over the arteries can be kept up in an extensive region through quite insignificant nervous twigs. We can thus understand how a flap of skin raised in a plastic operation in the human subject may have its circulation duly regulated through a narrow neck of attachment.

An experiment that greatly pleased Dr. Sharpey would seem to indicate that the vaso-motor function for the hind legs is also discharged by the most anterior part of the cord. A frog having been arranged as before described, the point of a fine needle, curved at the end, was introduced into the wound behind the occiput, so as to prick for an instant the divided