MEASUREMENT OF MASS MOVEMENT OF BLOOD 299 



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- 

 isiderable dilatation of other vascular parts, especially the splanchnic 

 irea. 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~^mimsh 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 aneurism, 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 

 cause great changes in the character of the pulse beat, does not decid- 

 edly affect the mass movement of the blood. In aneurism of the sub- 

 clavian artery, the bloodflow may be much greater in the corresponding 

 than in the opposite hand, even though the amplitude of the pulse is 

 very obviously diminished and the difference between the systolic and 

 diastolic pressures (the pressure pulse) is much less on the affected 

 than on the normal side. By ordinary clinical measurements, there- 

 fore, false estimates of bloodflow are quite likely to be made. These 

 results are no doubt owing partly to vasodilatation brought about by 

 pressure of the aneurism on the brachial plexus and partly to the 

 lower resistance to the flow of blood into the dilated subclavian. 



