What are the functions of the animals you rear--what the composition of their several parts--what the nature of the food they require--what the purposes it serves--what the proportions in which this or that kind of food ought to be given--what the changes, in the kind and proportion, to adapt it to the special habits and constitution of the animal, and the purposes for which it is fed? Are these questions deep? Yet they have all been thought over and long considered, and discussed and disputed about, and volumes have been written upon them; and the chemist, and the physiologist, and the anatomist have, unknown to you, all laboured zealously and without wearying, in your service. And what you now find so simple only proves how much their sciences have done for you. _They_ have fitted the machinery together, _you_ but throw in the fuel and keep up the steam. With the rearing of stock, and the improving of breeds, practical men are, or fancy themselves, all more or less conversant. How much warm and persevering genius, guided by purely scientific principles, has been expended upon our improved shorthorns and Leicesters! Are the whole lives of a Collins, or a Bakewell, or a Bates, nothing to have been devoted to pursuits like this? That these were practical men, and not scientific, and that what they have done is not a debt due by agriculture to science, is the saying of many. Men who have never read a book can do, by imitation, what the patient services and skill of other men discovered, and perfected, and simplified. But in this they are only stokers. The improvers were sound and cautious experimental physiologists, guided by the most fixed and certain principles of animal physiology; and it is the results at which these men arrived that have become the household words of the stokers of our day, who call them _practice_ in opposition to _science_. If science could forget her high duties to the Deity, and to the human race, she might leave you and your art to your own devices. Need we allude to the conditions of animal life--in a state of health, and in a state of disease; to the varied constitutions of different races and varieties; to the several adaptations of food, warmth, and shelter which these demand; and to the extensive course of study which is now required to furnish the necessary resources to the accomplished veterinary surgeon? Yet would any breeder be safe for a moment to invest his money in stock, in a country and climate like ours, had he not, either in books, or in his own head, or in that of a neighbouring veterinarian, the results at which the long study of these branches of knowledge, in connexion with animal health, had discovered and established?