102 THE DOG IN HEALTH. 



So that the whole subject may be grasped in a rational 

 manner, we remind the reader of certain well-established 

 physiological principles. 



All foodstuffs for animals are divisible into 



I. Organic. 



1. Nitrogenous : (a) albumins ; (5) albuminoids (as gela- 

 tin). 



2. Non-nitrogenous : (a) carbohydrates (sugars, starches) ; 

 (5) fats. 



II. Inorganic. 



1. Water. 



2. Salts. 



Every animal to remain in health must have all of the 

 above in its diet, as has been abundantly proved by experi- 

 ments i. e., the food must be chemically adequate. But, 

 in addition, food must be in such a form that the digestive 

 juices can attack it i. e., it must be physically suitable ; 

 and finally it must be suited to the peculiar organization 

 of each animal, which Nature expresses by what we term 

 liking i. e., the food in question must be craved. If a 

 diet fails in any of these respects it is not suitable. But 

 however good any article of diet in itself, a change is ab- 

 solutely essential from time to time. 



"We have no hesitation in saying that the whole art of 

 feeding dogs or other animals consists in the judicious 

 application of these few principles. 



It is well known that nearly all animals, and certainly 

 all dogs, will accept milk with avidity. Milk is a perfect 

 food because it meets all the above requirements. It is 

 what Nature has provided for all young mammals. 



But observation shows that wild mammals do not all 



