298 THE CIRCULATION OP THE BLOOD 



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

 centers concerned in vascular reflexes. Massage of the hand prior to 

 placing it in the calorimeter does not affect the flow. Massage of the 

 opposite hand, however, appears to cause an increase in flow. 



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 accompanied 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 but it must be used with very great care 

 that the temperature conditions are always the same; otherwise the re- 

 sults are apt to be misleading. 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 extreme degrees of these conditions, the vasoconstriction at the periph- 

 ery will assist in compelling more blood to pass through the lungs, so as 

 to make up for deficiency of 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 742), 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- 



