HEAT NEEDED TO EVAPORATE WATER DRUNK. 195 



be that the increase of water to be evaporated is 40 per cent, of 

 the additional water consumed. But Henneberg has recently 

 demonstrated that this amount is excessive, and declares that of 

 the water drunk not more than 7 to 17 per cent, is to be elim- 

 inated through perspiration, etc. 



Vogel made a series of experiments with sheep, and concluded 

 from one of these investigations that the average of evaporation 

 was 30.78 per cent, of water absorbed. Another experiment 

 gave 16.36 per cent., or an average for the two experiments of 

 23.57 per cent. But the ration under consideration contained 

 only 0.6 kilo of starch. This quantity is lost as a forage as it 

 has no equivalent -as work. An increase in the quantity of 

 blood without doubt results, but it remains to be proved 

 whether the increase in question means additional w r ork. 



According to Volkmann ^ G only of the force developed by 

 the heart is used, properly speaking, for the blood; the re- 

 mainder is utilized to overcome the resistance of friction in the 

 arterial and venous circulation. It remains to be demonstrated 

 whether this resistance is increased in consequence of a greater 

 quantity of blood put into circulation, or, on the contrary, is 

 diminished, owing to the greater fluidity of the blood. Up to 

 w r hat point can these two contradictory elements be considered as 

 compensating one for the other ? Maercker appears to lean to- 

 wards the theory of an increase in the necessary force at the time 

 of the circulation under consideration. As for the consumption 

 of albuminoids, it is, according to Mares, more and more pro- 

 nounced when the previous ration was deficient in these ele- 

 ments. This would be due to a large consumption of water, 

 for the simple reason that it destroys and decomposes the living 

 substances of the protoplasm. If this absorption of water is of 

 daily occurrence the weight of the animal fed may decline in a 

 very marked degree. In order to overcome this decomposition 

 and to reconstruct or build up the protoplasm, it becomes 

 urgent to feed to animals elements richer in albumen than 

 w 7 ould otherwise have been necessary, as neither the fatty sub- 

 stances nor the carbohydrates can meet the demand. 



Weisbeck has fattened cattle and has obtained the following 

 results, which show the influence of the excessive water 

 absorbed : 



