as internal, natural or non-natural."¹2 In another place he "We allow to the arteries the same motions which we says, concede to the heart-viz., a diastole and a systole, or return from the distended to the natural state; this much we be- lieve to be effected by a power inherent in the coats them- selves." 13
The direct object of Harvey in this passage is to show that the heart distends the arteries, and that they collapse by their own contractility; but, taken in conjunction with the other passages that have been quoted, it gives a fore- cast of what is now of such immense advantage to us- viz., a knowledge of "vaso-motor change."
He perceived the altered calibre of vessels; he saw this in both contraction and dilatation; he referred this to a power inherent in the coats themselves; he pointed out the relation between these changes and external conditions ; also between them and emotional excitement or depression, and yet again, to contingent internal circumstances.
A hundred and eighteen years after Harvey published his treatise on the Circulation, Robert Whytt, the President of the Royal College of Physicians, in the sister City of Edinburgh, wrote these words: "Some grow pale upon anger; which effect may be owing to a spasm, or con- tinued contraction of the small arteries of the face, by which the motion of the blood will be retarded;" and again, further on, "In blushing, the increased motion of the fluids through the vessels of the face is accompanied with a glow. . . .;" and yet again, "The sense of cold and shivering is owing to a spasmodic contraction of these vessels, in con- sequence of that irritation which the nervous system suffers from the febrile stimulus or the beginning inflammation."¹4
Disquisitions on the Circulation of the Blood, addressed to John Riolan, p. 128. 13 Page 113. 14 On the Nature, Causes and Cure of Nervous, Hypochondriac and Hys- terical Disorders, pp. 64, 221.
