284 THE CIRCULATION OF THE BLOOD 



Fever. — Since changes in the cutaneous circulation probably con- 

 stitute the chief factor in the derangement of the temperature-regu- 

 lating mechanism in fever (cf. page 723), it is evidently of great ad- 

 vantage to be able to measure such changes quantitatively. This has 

 been done by Stewart in several cases of typhoid fever and in one case 

 of pneumonia. In general it was found that the flow in the feet never 

 exceeded the normal flow, and was usually much below it. This ten- 

 dency to vasoconstriction seems to be carried into convalescence. For 

 practical reasons the handflow has not been so extensively studied. 

 This hyperexcitability of the vasoconstrictor mechanism at the periph- 

 ery is most naturally interpreted as a defensive reaction of the or- 

 ganism by which an increased supply of blood is imported to those 

 internal organs "which bear the brunt of the infection. When we con- 

 sider that in spite of this constriction of the periphery the blood pres- 

 sure is low and the pulse dicrotic, we must conclude that there is con- 

 siderable dilatation of other vascular parts, especially the splanchnic 

 area. A very practical application of these facts presents itself in con- 

 sidering the rationale of the cold-bath treatment for fever. If, for 

 example, we conclude that the cutaneous constriction is in the inter- 

 ests of an increase in the bloodflow to the organ on which the stress 

 of the infection falls, it will evidently be more rational to lower the 

 temperature by methods which will not diminish, and may even in- 

 crease, the cutaneous constriction than to do so by causing the vessels 

 to dilate. In other words, the use of antipyretics seems to be contra- 

 indicated, since they diminish the body temperature by causing vaso- 

 dilatation at the periphery with a consequent withdrawal of blood 

 from the seat of infection. 



Cardiovascular Diseases. — In cardiac cases the handflow is far more 

 apt to be markedly deficient where there is evidence of serious impair- 

 ment of the myocardium than in cases where a gross valvular lesion 

 exists but the heart action is strong and orderly. This indicates that 

 it is more serious for the force of the heart pump to be interfered 

 with than for its valves, particularly the mitral, to be leaky. Even 

 where there is considerable venous engorgement, the flow may be lit- 

 tle diminished. In untreated cases of auricular fibrillation the blood- 

 flow is subnormal. After the administration of digitalis the bloodflow 

 in such cases is often promptly and decidedly increased. 



As would be expected, arteriosclerosis is associated with a small blood- 

 flow, and the vasomotor reflexes are weaker than in normal persons. 



In aortic cmeurism, when the aneurism is of such a size as to cause 

 pressure on the subclavian artery or vein, there is a diminution in flow 

 of the corresponding hand, but aortic aneurism itself, although it may 



