MEASUREMENT OF MASS MOVEMENT OF BLOOD 283 



temperature of the water in the calorimeter has likewise a great influence, 

 and for the comparison of diiferent cases it is always important that the 

 room and calorimeter temperatures be stated alongside the results. Muscular 

 contractions, produced by moving the fingers in the calorimeter, cause a 

 marked increase in flow, accompanied by a diminished flow in the hand 

 that was at rest. A great diminution of flow results from constriction of 

 the arm of sufficient degree to obstruct the venous circulation ; and when 

 the constriction, as that caused by a blood pressure armlet, is increased to 

 between the systolic and diastolic pressures, extremely little blood flows 

 through the hand. 



By immersing the opposite hand or foot in hot or cold water, the blood- 

 flow through the observed hand increases or decreases, respectively. 

 The change may be of a temporary character, or it may persist through- 

 out the whole period of immersion of the hand. These reactions are due 

 to a vascular reflex, and observations of its sensitiveness are of value in 

 the study of the effects of lesions either of the nerve or of the nerve 

 centers concerned in vascular reflexes. 



Clinical Conditions which Affect the Bloodflow 



Even in cases where there is plenty of other evidence of curtailment 

 of flow, the measurement may be of importance either for detecting 

 an alteration in the vascular reflex or, by comparison of the two 

 hands, for demonstrating the relative degree of alteration in flow. In 

 acute inflammatory conditions affecting one hand, there is an increase 

 in flow on the affected side accompained by a marked curtailment on 

 the other side. This indicates that an increased flow in the infected 

 area is accompanied by a reflex vasoconstriction elsewhere, particu- 

 larly in the symmetrically placed part of the opposite side of the 

 body. In cases of nonbacterial inflammation of the hand, as in gout, 

 no sign of vasoconstriction may be observed. 



There are many clinical conditions in which Stewart's method re- 

 veals an alteration in bloodflow that would be unsuspected by the use 

 of ordinary clinical methods. It is for the investigation of these that 

 the method is of greatest value. The most important findings are as 

 follows: 



Anemia. The bloodflow in the hand may be much less than normal 

 in pernicious anemia and secondary anemia, and distinctly curtailed 

 in chlorosis. Since the minute volume of the heart is also increased 

 in these conditions, the vasoconstriction at the periphery will assist 

 in compelling more blood to pass through the lungs, so as to make up 

 for deficiency of blood. 



