From the last-mentioned principle, founded on long experience and observation, Cline inferred, and he has laid it down as an incontrovertible position, that the lungs should always be large; and Youatt expresses the same opinion. This is undoubtedly correct as to working beasts, the horse and the ox, which require full and free respiration, to enable them to sustain great muscular efforts. But later physiologists have assumed, perhaps from closer and more accurate observations, that the fattening propensity is in the ratio of the smallness of the lungs. Earl Spencer has observed, that this is fully shown in the pig, the sheep, the ox, and the horse, whose aptitude to fatten and smallness of lungs, are in the order enumerated. This position is further illustrated by the different breeds of the same classes of animals. The Leicester sheep have smaller lungs than the South Down; and it has been found, that a number of the former, on a given quantity of food, and in the same time, reached 28 lbs. a quarter, while the South Downs with a greater consumption of food, attained in the same period, only 18 lbs. The Chinese pigs have much smaller lungs than the Irish, and the former will fatten to a given weight, on a much less quantity of food than the latter. (_Playfair._) The principle would seem to be corroborated by the fact, that animals generally fatten faster in proportion to the quantity of food they consume, as they advance towards a certain stage of maturity; during all which time, the secretion of internal fat is gradually compressing the size, by reducing the room for the action of the lungs. Hence, the advantage of carrying the fattening beast to an advanced point, by which not only the quality of carcass is improved, but the quantity is relatively greater for the amount of food consumed. These views are intimately connected, and fully correspond, with the principles of RESPIRATION IN ANIMALS. From careful experiments, it has been found that all animals daily consume a much larger quantity of food than the aggregate of what may have been retained in the system, added to what has been expelled in the f[oe]ces and urine, and what has escaped by perspiration. Boussingault, who combines the characteristics of an ingenious chemist, a vigilant observer, and a practical agriculturist, made an experiment with a "milch-cow and a full-grown horse, which were placed in stalls so contrived that the droppings and the urine could be collected without loss. Before being made the subjects of experiment, the animals were ballasted or fed for a month with the same ration that was furnished to them, during the three days and three nights which they passed in the experimental stalls. During the month, the weight of the animals did not vary sensibly, a circumstance which happily enables us to assume that neither did the weight vary during the seventy-two hours when they were under especial observation.