ANIMAL HEAT. 517 



The actual demonstration that more water is ever discharged from the body than can 

 be accounted for by the water of the ingesta, or by water simply withdrawn from the 

 blood rendering this fluid more dense, presents very considerable but not insurmountable 

 difficulties. A process that would be open to few objections, provided all of the elements 

 used in the calculations were accurate, is the one which we have attempted to employ in 

 cases of loss of weight. This process is the following : 



Take the weight of a man at the beginning of the experiment, calculate accurately 

 the weight of the ingesta for a certain period, and add this latter to the weight of the 

 body. This forms a sum total from which the following quantities are to be deducted: 

 Take the weight of the urine and feeces passed during the time of the experiment; add to 

 this the weight of the carbon contained in the carbonic acid exhaled, which' carbon car- 

 ries with it a portion of the inspired oxygen ; add both of these to the weight of the body 

 taken at the close of the experiment; the difference will give the amount of water dis- 

 charged by the lungs and skin. Having thus the quantity of water discharged by the 

 lungs and skin, to ascertain the total quantity of water discharged from the body, we 

 have to add the water contained in the urine and fasces. We then carefully estimate the 

 amount of water contained in the ingesta and can compare the amount of water dis- 

 charged with the quantity taken. In Pettenkofer's chamber, in which a man may be 

 confined and all of the excreta be estimated, these calculations could be made with suf- 

 ficient accuracy, and the only uncertain element in the problem would be as to whether 

 or not the blood became modified in density or volume. In the following calculation, we 

 were forced to estimate the amount of carbon eliminated, but we endeavored to correct 

 this estimate by an indirect method. 1 The subject of the experiment was the person 

 mentioned in Observation 1, and the investigations described were continued for five days, 

 during which period he walked 317i miles. The following is a summary of the results: 



Observation upon the Ingress and Egress of Water. 



Ounces. 



Body-weight at the beginning of the observation 1,907-20 



Weight of the ingesta for five days 857'34 



Total 2,764-54 



Weight of the urine and faeces for five days 220 - 47 



Carbon eliminated for five days, estimated at 10 ounces per day. . . . 50*00 

 Body-weight at tae end of the five days (showing a loss of 55*2 ounces) 1,852*00 



2,122-47 



Water eliminated by the lungs and skin 642*07 



Water contained in the urine and faeces. 208*89 



Total water discharged 850*96 



The water of the food and drink taken for the five days was carefully estimated, and 

 it amounted to 788*18 ounces. This deducted from the total quantity of water discharged 

 gives an excess of 62*78 ounces discharged for five days, or a daily excess of 12*56 ounces. 



The heat- value of the hydrogen required to form one ounce of water is equal to 432-5 



1 As stated in the text, we were forced to estimate the amount of carbon discharged, bnt preferred to put it too 

 high rather than too low. Ten ounces per day is a very high estimate for a man weighing 115$ pounds. The follow- 

 ing indirect calculation of the probable sources of carbon shows that this estimate is certainly not too low. We 

 < ii ulate the total carbon of the food as amounting to about twenty-five ounces. To this we add the carbon of forty- 

 eight ounces of muscular tissue consumed (5-23 ounces), and of 7*2 ounces of fat, both loss of weight (5-69 ounces). 

 This gives about thirty-six ounces of carbon for five days. From this we deduct nine ounces of carbon discharged in 

 the urea, wtiidi loaves twenty-seven ounces for five days, or 5'4 ounces per day. If we calculated that the entire 

 toss of weight of 55-2 ounces should be estimated as fat which is very improbable from the condition of the subject 

 on beginning the walk and the discharge of a considerable quantity of nitrogen from the body over and above the 

 nitrogen of food -we should have about fifty-nine ounces of carbon for five days, or 11*3 ounces per day. The last- 

 named quantity would make very little difference in the results given above. 



