The causes of obesity are numerous. It is often hereditary or constitutional, the inclination being derived from either parent. This tendency is seen not only in individuals but in nations: e.g., the Dutch are as stout, as the Americans are proverbially thin. Over-feeding will induce fat, and so will the habit of taking too much fluid. The obese are not always great eaters: but they invariably drink a great deal, even though it be only water. Farinaceous and vegetable foods are fattening, and saccharine matters are especially so. The instance of the slaves in Italy, who got fat during the grape and fig season, has been quoted by Galen. In sugar-growing countries the negroes and cattle employed on the plantations grow remarkably stout while the cane is being gathered and the sugar extracted. During this harvest the saccharine juices are freely consumed; but when the season is over, the superabundant adipose tissue is gradually lost. And then amongst other causes we must reckon insufficient exercise, long continued pros perity and ease of mind, indulgence in too much sleep, and an absence of the sexual appetite. Eunuchs are generally described as being flabby and fat; whilst amongst the lower animals, fattening is readily produced after the removal of the testicles or ovaries. The way in which the same fact can be made to tell in favour of two opposing theories is curiously illustrated by two writers on this subject. Thus, Wadd cites the butchers as examples of corpulence, alleging that their excellent condition is due to animal food. He speaks particularly of the advantages of the “butcher's steak; " and does not believe that these men and their wives owe their good looks to “the effluvia of the meat."* Dancel also speaks of the frequency with which the members of the same class become obese; but he says it is because the butchers eat meat and plenty of vegetables, while their wives generally prefer vegetables to animal food. He has no faith in the opinion that their embonpoint has some connection with the atmosphere of nutritive animal odours in which they live. 

Fats are obtained abundantly from both the animal and vegetable kingdoms. Their predominating elements are carbon and hydrogen. They never contain nitrogen, except as an accidental ingredient. They are made up of three closely allied bodies; viz., stearin (from otéap = suet ], margarin ( from its lustrous appearance, pápyapov = a pearl ], and olein [ oleum = oil ] which is Huid. When fatty matters are heated with the hydrated alkalies, they undergo saponification, during which process a viscid sweet fluid glycerine ( dukùç = sweet ] -is yielded. Now several physiological studies lead to the conclusion that oils and fats may not only be formed in the system from food which contains it ready prepared, but also from the chemical transformation of starch or sugar. Many experiments have been performed on geese, ducks, and pigs, which have proved that these animals accumulate much more fat than could be accounted for by that present in the food. M. Flourens had the bears at the Jardin des Plantes fed exclusively on bread, and they became excessively fat. Magendie, in making experiments on the forage of horses, found that these animals constantly returned more fat in their excrements than their food contained. And several authors have shown that bees form wax, which strictly belongs to the group of fats, when fed exclusively on purified sugar. If with foods of this nature the animals be subjected to a warm atmosphere and allowed but little room for movement, the adipose tissue rapidly gets increased. At Strasburg, the place of all others most noted for its pâtés de foie gras, the geese are fatted by shutting them up in coops within a room heated to a very high temperature, and stuffing them constantly with food. Here all the conditions for insuring obesity are resorted to --- viz. external heat, obscurity, inactivity, and the cramming of the animals with nourishment.