1 90 NUTRITION OF FARM ANIMALS 



proportions that their solution possesses nearly the maximum 

 capacity for the preservation ol neutrality, while they also, 

 particularly the phosphates, serve as a means of elimination of 

 an excess of acid through the kidneys in the form of the acid 

 phosphates of the urine. 



272. Other functions of ash. The three general functions 

 just enumerated by no means exhaust the list of offices performed 

 by the ash ingredients. Iron, for example, is an essential in- 

 gredient of haemoglobin, the coloring matter of the red blood 

 corpuscles, which is the vehicle by which oxygen is distributed 

 throughout the body (191). Although contained in the body 

 in relatively minute amounts, this element is, therefore, one of 

 prime necessity. lodin appears to be an essential ingredient 

 of the thyroid glands, and although we are ignorant of its 

 exact functions it is known that the absence of these glands, or 

 their failure to function, gives rise to serious disturbances 

 (goitre, myxcedema). Recent investigations seem to indi- 

 cate that manganese and boron, and perhaps other elements 

 not heretofore regarded as essential, may have important 

 functions as catalysts in plants and perhaps, therefore, in 

 animals also, although this is at present a conjecture. It is 

 likewise possible that other elements present in small amounts 

 may later be shown to have physiological functions. 



273. Functions of water. Its very familiarity tends to make 

 us overlook the striking nature of the fact that life as we know 

 it is impossible in the absence of water. If protoplasm may be 

 regarded as a collodial solution, one may almost say that life 

 is possible only in aqueous solutions. 



Some reasons for this are fairly obvious. The phenomena of 

 osmotic pressure and ionization, for example, whose impor- 

 tance has just been indicated, are substantially solution phe- 

 nomena. It is possible also that there are more fundamental 

 reasons for this striking fact. Certainly the larger share of our 

 present chemical knowledge relates to the chemistry of either 

 aqueous solutions or gases, two states resembling each other 

 in many respects and in which chemical action seems to occur 

 most readily, if indeed it ever takes place in the solid state. 

 Moreover, it has been shown that some reactions, at least, in 

 which water is not commonly regarded as concerned, are 

 dependent upon the presence of minute amounts of this sub- 



