PRACTICAL EXERCISES 219 



pelvis at the apices of the pyramids, or it may be only in the cortex. 

 The urine is greenish. If some methylene blud has been injected after 

 the heart ceased to beat, the bloodvessels, particularly in the mesentery, 

 may be beautifully mapped out by the pigment. This is not the 

 case if the last injection took place before death, since the methylene 

 blue is rapidly reduced by living tissues to a colourless substance, 

 leuco-methylene blue. 



31. Measurement of the Blood-Flow in the Hands. Arrange the 

 calorimeters as in Fig. 108. The thermometers in the calorimeters 

 should be graduated in tenths of a degree, so that by means of the small 

 lenses or ' readers ' which slide on the stems hundredths of a degree 

 can be estimated. Where it is desirable that a number of students 

 should make observations in as short a time as possible, one calorimeter 

 can be allotted to each subject, the other hand being kept in the pocket 

 or covered with a glove if the room is cool, so as to avoid reflex vaso- 

 motor interference. A felt collar is chosen which fits the wrist closely. 

 A horizontal pencil-mark is made at the lower edge of the styloid 

 process of the ulna, and another parallel mark at a distance above this 

 slightly greater than the thickness of the collar. When this second 

 mark is just kept in view above the collar with the hand in the 

 calorimeter, the first (lower) mark will be jiut below the level of the 

 lid. A large bath holding 20 or 30 litres or niore (a clean ' garbage ' 

 or ' offal ' can is suitable) is filled with water at about 32 C. The 

 exact temperature is not important, but it should be about the same 

 in all measurements which are to be compared. An ordinary ther- 

 mometer graduated in degrees is all that is necessary for reading the 

 temperature of the bath. The calorimeters are now filled from the 

 bath. They are conveniently made of such a size that 3 litres of water 

 and the hand can be contained in them without any slopping over 

 when the water is stirred. Time is saved by having a metal flask 

 which just holds the quantity of water that goes into each calorimeter. 

 The orifices of the calorimeters are closed by felt discs. The subject, 

 sitting in a high chair placed between the calorimeters, now immerses 

 his hands in the bath to a point between the two marks. The fingers 

 are kept spread. The bath is occasionally stirred. An ordinary ther- 

 mometer suspended at the back of the chair gives the room tempera- 

 ture. After ten minutes the hands are withdrawn from the bath, the 

 wrists rapidly dried with a towel, the hands at once introduced into the 

 calorimeters, and the felt collars adjusted round the wrists. The sub- 

 ject leans back comfortably in the chair, allowing the arms to hang 

 down without effort. The fingers are kept slightly spread. The ob- 

 server sits on a low seat behind the subject, and reads the thermometers 

 from time to time, always after stirring the water well with goose- 

 feathers passing through the stirring-holes in the lid. The readings 

 can be made at intervals of a minute, two minutes, or any interval 

 which is convenient. At the end the hands are quickly withdrawn, 

 the felt discs put over the orifices, and the water vigorously. stirred for 

 ten or fifteen seconds before the thermometers are read. In this way 

 any errors due to imperfect stirring or to accidental contact of the 

 hands with the thermometers are eliminated. 



The volume of each hand is now measured by immersing it exactly 

 to the lower mark in water contained in a glass douche-can connected 

 by a short rubber tube with a pipette furnished with a side-tube at its 

 lower end. The lowest graduation on the burette (50 on a 50 c.c. 

 burette) is brought level with the water before the hand is immersed, 

 While the hand is being held steadily and vertically in the water by 

 an assistant, the level of the water in the burette is read off. All that 



