REPORTS ON DIFFERENT DESCRIPTIONS OF FOOD FOR STOCK. 53 



able fact, that many of our most deadly poisons differ but little 

 in composition from well-known substances which are confessedly 

 highly nutritious. 



In estimating theoretically the comparative nutritive values of 

 different kinds of food, physiology as well as chemistry must do 

 its part. The chemist must not only make known to us the 

 elementary composition of the foods, but he must also show the 

 states of combination in which they exist ; and the physiologist 

 must not only tell us the states of combination in which these 

 elements are most readily assimilated, but he must also show the 

 proportions of one to another required for the formation of bone, 

 muscle, fat, and milk, respectively. This accomplished, it would 

 become as easy a calculation to show the quantity of a given 

 food required to produce a certain amount of bone, muscle, 

 fat, or milk, as it now is to show the quantity of a given coal 

 required as food to the iron horse to produce a certain amount 

 of work. It is almost superfluous, however, to remind the reader 

 how very far indeed either chemistry or physiology is from 

 having reached this acme of perfection, or to state that the 

 method of investigating the comparative nutritive values of 

 different kinds of food, on which most reliance can in the mean- 

 time be placed, is unquestionably practical experiments. It 

 should not be forgotten, however, that experiments on the feed- 

 ing of animals are peculiarly liable to inaccuracies, from the ease 

 with which animal functions are disordered, and the difficulty 

 of discovering the presence of minor disorders. All animals 

 will, at times, eat more or less heartily than usual. A milch cow 

 will suddenly give a pound or two more or less milk than usual 

 for a day or two without any apparent cause, and a fattening 

 beast will sometimes actually lose weight, or at least will gain 

 nothing, when feeding as well as usual, and apparently in full 

 health. It is exceedingly difficult, too, if not impossible, to get a 

 sufficient number of animals whose constitutions are exactly alike : 

 some assimilate a much larger proportion of their food than others, 

 and occasionally the same food is found to produce different 

 effects on different animals, so that all such experiments, before 

 we are warranted in arriving at any definite conclusions, must 

 be repeated many times. 



On January 16th 1864, four milch cows, four feeding beasts, 

 four queys (heifers) rising two years old, and four stirks rising one 

 year old, all of the Ayrshire breed, were put up in pairs and fed 

 alike till February 3d, particular notice being taken of the quan- 

 tity of food which each lot of two could consume per day. The 

 quantities at last fixed upon for each lot, and the hours at which 

 they were given during the whole time the experiment lasted, 

 will be found in Table I. 



