516 NUTRITION". 



Observation 2. November 22, 1878, we made an experiment, fasting for twenty-four 

 hours, beginning the observations for the twenty-four hours nine and one-quarter hours 

 after the last meal. In this experiment, the urine of the twenty-four hours was collected 

 and analyzed, and we drank during this period twenty ounces of water. The loss of 

 weight of the body was fifty-six ounces. The calculations of the sources of heat, exclud- 

 ing the possible generation of heat by the union of oxygen with hydrogen, were made by 

 estimating the heat-value of the carbonic acid eliminated by the lungs and of the urin- 

 ary nitrogen. Estimated in this way, the total heat represented by the nitrogen elimi- 

 nated in the urine and by the carbonic acid was equivalent to 12,436-79 heat-units. The 

 estimated heat produced by the body for the same period was equivalent to 17,904*00 heat- 

 units, leaving 5, 467*21 heat-units, or about one-third of the heat produced, unaccounted for. 



Observation 3. November 30, 1878, we made another experiment in which the heat- 

 value of the food taken for twenty-four hours was estimated, the weight of the body 

 remaining stationary. In this observation, the total heat-value of the food was equivalent 

 to 14,979'! 5 heat-units, and the heat produced by the body was equal to 17,880-00 heat- 

 units, leaving 2,900'85 heat-units, or about one-sixth of the heat produced by the body, 

 unaccounted for by the food. 



The results of these observations naturally led to a consideration of the theory first 

 proposed by Lavoisier and Laplace, that oxygen may unite with hydrogen in the body 

 to form water and produce heat. Thus far, however, there has been no experimental 

 demonstration of the actual production of water in the animal economy. In the ex- 

 periment in which we fasted for thirty-three hours, during twenty-four hours of which 

 no food was taken after the digestion of articles taken about nine hours before had 

 been completed, it was estimated that about thirty-two ounces of water were discharged 

 by the lungs and skin, and thirty-four ounces of water were actually eliminated by 

 the kidneys, making a total discharge of water of sixty-six ounces. During this period, 

 twenty ounces of water were taken, leaving about forty-six ounces over and above the 

 quantity ingested. The loss of weight was fifty-six ounces, of which we may estimate 

 a loss of about ten ounces in solid matters in the urine and in carbon by the lungs. 

 The question now is whether this loss of forty six ounces of water was simply a dis- 

 charge of water already formed, from the blood and the watery parts of the tissues, or 

 whether it is to be attributed in part to water actually formed in the body by a union of 

 oxygen and hydrogen. If the watery parts of the body be actually deficient in quantity, 

 there is usually a sensation of thirst. There was no suffering from thirst, and, indeed, 

 we drank rather more water than was desired. Recent experiments by Valentin, Panum, 

 Colin, and others, have shown, in opposition to the previously-received opinions, that 

 abstinence from food has very little effect in diminishing the volume of the blood. This 

 fact, taken in connection with the absence of thirst during the twenty-fours of fasting, is 

 favorable to the view that all of the excess of water discharged did not come directly 

 from the blood. 



If water be actually produced in the economy by a union of oxygen and hydrogen, what 

 is the probable source of these two elements? There is no deficiency of hydrogen in the 

 body, and, if it be used to form water which is discharged, there would be loss of weight 

 when no food is taken, and it would be supplied by the food under ordinary conditions of 

 nutrition. There is no deficiency of oxygen in the body itself, and the oxygen discharged 

 in urea represents only about one-third of the proportion of oxygen contained in the 

 nitrogenized constituents of the body. Of the oxygen taken into the lungs, about eighty- 

 six per cent, only is returned in combination with carbon to form carbonic acid, leaving 

 fourteen per cent, to form some other combination in the body, possibly a union with 

 hydrogen. There is, indeed, little oi' no difficulty in accounting for the elements to form 

 water in the body, if it can be shown that more water is discharged from the organism 

 than is taken with the ingesta, and that the excess thus discharged does not come simply 

 from the watery parts, producing an actual deficiency of water in the body. 



