34 DIGESTION AND FOOD. 



are likewise met with in solids and fluids, and it has been 

 supposed that it is to these that the alkalinity of the blood 

 and other fluids is due. 



Carnivorous animals receive a proper supply of phosphates 

 from animal food, and especially from bones, whereas 

 vegetable feeders obtain them largely from the grasses. 

 It is owing to the latter circumstance that the value of 

 phosphatic manures has been recognised; and in proportion 

 that the phosphates are soluble and capable of nourishing the 

 plants, are they valuable in fertilizing the land. There are many 

 districts in the south of Scotland and north of England, 

 where, by a judicious combination of phosphatic and ammo- 

 niacal manures, a disease attended with softening of the 

 bones, and termed " the Stiffness," or " the Cripple,"* might 

 be prevented the phosphates being essential to supply a 

 want in the plants, and the ammoniacal principles favouring 

 the full development of a luxuriant vegetation. 



Dr Lankester refers to an interesting feature in the history 

 of phosphate of lime. He says : 



" Liebig has shown that it is highly probable that one 

 of the causes that led to the destruction of the great cities of 

 antiquity was the difficulty of obtaining a supply of food for 

 their inhabitants. As they went on increasing, the soils in 

 the immediate vicinity became exhausted of the phosphate, 

 and, at last, refused to grow food at all. As the means of 

 transit were not so perfect as they are now, men found it 

 easier to go to places where the virgin soil produced abund- 

 ance of food, than to bring the food to their cities. Hence 

 the migrations of peoples, and the desolation of once busy 

 cities. In America this process is going on every day. 

 When a district is exhausted of its mineral food, the farmer 



* See Edinburgh Veterinary Review, vol. iii. 



