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TEXT-BOOK OF PHYSIOLOGY 



These calorimeters consist of two parts, one for the collection of the 

 heat liberated by the subject of the experiment, and the other for the col- 

 lectidn of the carbon dioxid and water exhaled and for the measurement 

 of the oxygen consumed. Means are also provided for the collection of the 

 urine and feces when necessary. 



The first part of the calorimeter consists, Fig. 201, of a chamber of sufficient 

 size with metallic walls, copper and zinc so arranged as to prevent either 

 absorption or radiation of heat, in other words that they will be heat- 

 proof. At one side there is a door of sufficient size to admit the subject 

 as well as a window to admit light. The heat dissipated by the subject of 

 the investigation is taken up by a current of water of even but low tem- 

 perature and flowing constantly under a steadily acting pressure through a 

 copper pipe of 6 mm. internal and 10 mm. external diameter. The tem- 

 perature of the water is determined before it enters and after it leaves the 



Oxygen j Rotary pump 



H X SO+ Soda Lime 

 FIG. 201. DIAGRAM TO SHOW THE PRINCIPLE OF THE AT WATER-BENEDICT CALORIMETER. 



chamber. The amount of water passing through the tube in a given time, 

 is collected and weighed. The difference in temperature, multiplied by 

 the weight of the water gives the amount of heat dissipated by the individual. 

 To facilitate the absorption of the heat a large number of copper discs 5 

 centimeters in diameter are soldered to the water pipe at a distance of 5 

 millimeters from one another. As the absorption pipe is some 5 meters 

 in length, the area presented for absorption approximate about 4.7 square 

 meters. The heat thus absorbed is soon conducted to the water followed by a 

 rise in its temperature. Inasmuch as many experiments extend over a 

 period of several days or more, special arrangements have been devised for 

 the introduction of food which, however, do not interfere with the accurate 

 working of the calorimeter. The door of the food aperture is provided with 

 glass for the transmission of light into the chamber. In some calorimeters a 

 bed is provided, in others a chair as well as devices which enable the subject 

 to perform a measurable quantity of mechanical work. 



