678 



PHYSIOLOGY OF THE DOMESTIC ANIMALS. 



urea remained constant. He was then allowed to fast for ten days and 

 the urea estimated (A). He was then fed with the same food, and then 

 for ten days received nothing but one hundred grammes of fat (B). 

 The following results were obtained : — 



Last day of feeding, 



1st day of fasting, 



2d 



3d 



4th 



5th 



6th 



7th 



8th 



9th 



A. 



Urea in 



Grammes. 



. 110.8 



. 26.5 



. 18.6 



. 15.7 



. 14.9 



. 14.8 



. 12.8 



. 12.9 



. 12.1 



. 11.9 



B. 



Urea in 

 Grammes. 



111.8 

 27.2 

 16.3 

 14.1 

 12.9 

 12.4 

 10.8 

 10.5 

 10.7 

 10.2 



Through the administration of the fat 14.1 grammes of albumen 

 escaped destruction, or, as Voit expresses it, was " saved." 



Water also exerts a considerable influence on the destructive 

 processes in starvation, a large consumption of water always increasing 

 the excretion of urea. This evidently points to an increased decom- 

 position of proteids, and not a mere increase in the amount of urea 

 washed out, since it has been proved that when water is withheld there 

 is no accumulation of urea in the economy. 



On the other hand, the most violent muscular movements during 

 starvation produce but little appreciable increase in the amount of urea 

 eliminated, thus showing that the combustion of albuminoids is not the 

 source of muscular force. 



In earlier times, with the exception of the lime salts in the bones, 

 the inorganic substances found in the animal body were regarded as 

 secondary in importance and, in fact, almost as accidental constituents. 

 Liebig and his scholars first recognized the importance of these bodies; 

 especially Na, CI, Ca, K, Mg, Fe, and P 2 6 are absolutely essential for 

 the health of the animal body. If these bodies are removed from the 

 food, or even reduced in amount, the animals rapidly perish, even though 

 supplied with an abundance of organic food. 



This disturbance of nutrition is not, as was first supposed, because 

 the removal of salts interferes with the activity of the digestive secre- 

 tions, since digestion and absorption, even under such circumstances, is 

 perfectly carried out, but because salts are removed constantly from the 

 body, and if they are not supplied in food tlie animal rapidly perishes, as 

 these salts are essential to the various functions of the economy. 



Forster fed a dog with food which was as much as possible freed 

 from salts; as proteids, he used the residue from the manufacture of 

 beef extracts, butter freed from salts, potato-starch washed with HC1, 

 and distilled water. 



