MEASUREMENT OF MASS MOVEMENT OF BLOOD 297 



ing the change of temperature in the calorimeter for a certain period 

 of time after the hand has been removed from it. 



The Normal Flow 



The results are calculated on the basis of grams of blood flowing 

 through 100 c.c. of tissue in one minute. The volume of the hand or foot 

 is ascertained by placing it in water contained in a small-sized irrigation 

 can, the tube of which is connected with a burette. The height to which 

 the water rises in the burette is noted, and after withdrawing the hand, 

 water is added from a graduate to the irrigation can until the same 

 height is reached on the burette. The number of cubic centimeters re- 

 quired gives the volume of the hand. In a normal, healthy individual 

 the average flow in the hand is from 12 to 13 gm. for the right hand, 

 and about half a gram less for the left. This difference between the two 

 hands corresponds, of course, with their relative degree of development. 

 The average foot flow is much less, and varies according to whether the 

 patient is sitting up or lying down while the measurement is being made. 

 In a normal individual, while lying down, it was 5.11 gm. in the right 

 foot and 5.23 gm. in the left, per 100 c.c. of foot; but only 2.96 gm. for 

 the right and 4.1 gm. for the left foot, while sitting up. By extended ex- 

 perience with the method we have found that the bloodflow is very 

 greatly influenced by the average outside temperature. Although the 

 outside influence may be diminished somewhat by spending some time 

 indoors before the measurement is actually made, this does not entirely 

 remove the outside influence. 



The Physiological Causes for Variations in Bloodflow. As above indi- 

 cated, the most marked of these is probably the temperature of the 

 room. The temperature of the water in the calorimeter has likewise a 

 great influence, and for the comparison of different cases it is always 

 important that the room and calorimeter temperatures be stated along- 

 side the results. Muscular contractions, produced by compressing 

 a dynamometer by the fingers, cause a decided increase in flow. 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 



