342 NUTRITION OF FARM ANIMALS 



alkaline ash in discussions of both human nutrition and that 

 of domestic animals. Doubtless the point is an important one 

 but the assumption that all excess of acid over basic elements 

 in the diet should be avoided seems hardly warranted, especially 

 as regards maintenance. The fact that the body is to a certain 

 extent provided with a means of defense against excessive acids 

 through its ability to neutralize them by means of ammonia 

 and through the power of the kidneys to separate acids and 

 bases is sufficient to show that an excess of acid-forming ele- 

 ments in the feed is not necessarily injurious. It is only when 

 the excess is so large as to exceed the capacity of these regulative 

 arrangements and when it therefore begins to draw on the 

 fixed bases of the body, or possibly when it causes the produc- 

 tion of large quantities of ammonia, that it becomes a source of 

 danger. 



433. Alkali ratio of ash. As indicated in previous para- 

 graphs, the ratio of potassium to sodium in a feeding stuff may 

 have an important bearing on the losses of ash from the body. 

 It was there stated that while a surplus of potassium salts re- 

 sorbed into the blood is promptly disposed of by excretion 

 through the kidneys, it may carry along with it more or less 

 sodium, so that a ration relatively rich in the former may tend 

 to impoverish the body in the latter. Such a loss of sodium 

 from the body, it would appear, might have serious indirect 

 effects if continued long enough to cause a draft on the stock of 

 sodium in the skeleton. Such a draft, as already said (428), 

 involves the solution of a corresponding amount of the total 

 ash of the skeleton, so that the bones would be impoverished 

 in other ingredients, especially calcium and phosphoric acid, as 

 well as sodium. In fact it has been found that fodders that 

 cause malnutrition of the bones resulting in the disease known 

 as rickets (Rachitis) usually show a misproportion of potassium 

 to sodium. Zuntz 1 cites the following comparisons of the ash 

 of normal hay with that of hays causing the disease. Along 

 with a somewhat greater ratio of phosphoric acid to calcium, 

 the injurious hays show a very striking difference in the 

 alkali ratio, as appears from the following table to which 

 the corresponding figures for cow's milk have been added for 

 comparison : 



1 Jahrb. Deut. Landw. Gesell., 1912, p. 577. 



