PRACTICAL EXERCISES 



219 



is necessary to get the volume of the hand is to pour water into the 

 can from a graduated measure after withdrawal of the hand until the 

 same level is reached. Or the value of a division of the burette can 

 be determined once for all. The burette is simply used as a transparent 

 scale. When the two hands are successively measured, the small 

 amount of water removed by the first is automatically restored by 

 dipping the second into a separate vessel of water, and putting it wet 

 into the douche-can. The rectal umperature should now be obtained.. 

 The temperature of the arterial blood entering the hand is taken as 

 o'5 C. below that of the rectum. If only the mouth temperature can 

 be got, the thermometer should be put in a second time without shaking 



Fig. 108. Calorimetric Method of measuring Blood-Flow in Hands. 



down to see if it rises any more. The mouth temperature is taken as 

 equal to the arterial blood temperature. 



After thorough stirring, the calorimeter temperatures can now be 

 read again. The two being noted, the amount of cooling of the calor- 

 imeters can be determined. This has to be added to the actually 

 observed rise of the thermometers during immersion of the hands. 



Suppose an experiment yielded the following data: Rise of ther- 

 mometer in a calorimeter in twenty minutes during immersion of a hand 

 in it, 1*0 C. ; temperature of calorimeter at beginning of the twenty 

 minutes, 3i'o C. ; at end of twenty minutes, 32-0 C. ; cooling of calor- 

 imeter in twenty minutes, o'i C.; water in calorimeter, 3,000 c.c.; 



