in anatomy, an oily concrete substance depo- fitted in different parts of animal bodies.

Strong exercise, supernatural heat, an acrimonious state of the juices, and other like causes, by which the oily parts of the blood are attenuated, refolved, or evacuated, prevent the generation of fat: labours of the mind also have this effect, as well as labour or in- temperature of the body. Hence rest and plentiful food are sufficient to fatten brutes; but with men it is often otherwise. It is surprising how soon some birds grow fat; ortolans in 24 hours, and larks still sooner.

Fats may be divided, from their consistence, into three kinds: (1.) The soft and thin, which grow perfectly liquid in a very small heat. (2.) The thick and consistent, which liquify less readily; and, (3.) The hard and firm, which require a still stronger heat to melt them. The first is called Pinguedis; the second, Auxungia; and the third, Adeps, as taken from the animals; and Sebum, or Sevum, when freed from the skins, &c. This use of the names, however, is not constant, some employing them differently.

A great number of fats have been kept in the shops, for making ointments, plasters, and other medicinal compositions; as hogs-lard, the fat of the boar, the fox, the hare, dog, wild cat, Alpine mouse, beaver; that of hens, ducks, geese, storks; of the whale, pike, serpents, viper, &c. as also human fat.—In regard to all these kind of substances, however, much depends upon the manner of purifying or trying, and of keeping them.

To obtain fat pure, it must be cut into pieces, and cleaned from the interposed membranes and vessels. It must then be cleansed from its gelatinous matter by washing with water, till the water comes from it colourless and insipid; it is afterwards to be melted with a moderate heat in a proper vessel with a little water; and it is to be kept thus melted till the water be entirely evaporated, which is known by the discontinue- ance of the boiling, which is caused by the water only, and which lasts till not a drop of it remains: it is afterwards to be put into an earthen pot, where it fixes; then it is exceedingly white, sufficiently pure for the purposes of pharmacy or chemical examination.

Fat thus purified has very little taste; and a weak, but peculiar, smell.

Mineral acids exhibit the same phenomena with fat, as they do with the fixed sweet oils of vegetables, which contain nothing gummy or resinous, and which do not dry. Such is the oil of ben, oil of olives, and all those which chemists call fat oils.

Alkalis dissolve fat, as they do these oils, and form a similar soap. Fat contains no principle so volatile as to be raised with the heat of boiling water. It does not inflame, but when heated in open air to as to rise in vapours. Lastly, by age it contracts an acid and rancid quality.

When fat is distilled with a heat superior to that of boiling water, which must therefore be done in a retort and in a naked fire, first an acid phlegm arises, and a small portion of oil which remains fluid. As the distillation continues, the acid becomes stronger, and the oil thicker, and at last it congeals in the receiver. No other principle arises during this distillation: and, lastly, when the retort is red, nothing remains but a very small quantity of that kind of coal which cannot be burnt without very great difficulty. See Coal. If the congealed oil which is found in the receiver be again distilled, more acid is obtained, and an oil which does not congeal; and thus, by repeating the distillations, the oil is more and more attenuated. While it is thus deprived of its acid, it acquires a more and more penetrating smell; and thus, by distillation alone, it may be rendered as volatile as essential oils, and capable of rising with the heat of boiling water.

Fat, and all other analogous oily matters, cannot be heated sufficiently to be raised into vapours, without suffering a considerable alteration, and even decomposition. The vapours which rise from it, when heated in open air, are the same as those which rise when distilled in close vessels. They consist of acid and attenuated oil. This acid is remarkably penetrating, acid, and volatile; it irritates and inflames the eyes, the throat, and lungs; it makes the eyes shed tears, and excites a cough as much as volatile sulphureous acid does, although its nature be very different.

When fat is in its natural state, and has not yet suffered any alteration, its acid is so well combined with its oily part, that none of its properties can be perceived. Thus fat, in good condition, is very mild, and used successfully in medicine, particularly externally, for its lenient quality: but, notwithstanding its great mildness, before it has been heated sufficiently to decompose it, and while it is yet fresh, it becomes exceedingly acid, irritating, and caustic, when its acid is partly disengaged by fire or by time.

When fat is become very rancid, not only its medicinal effects, but also many of its essential properties, are totally changed, particularly its property of resisting the action of spirit of wine: for this menstruum, which does not affect pure and unchanged fat, dissolves some portion of fat which has been strongly heated, or which has become rancid. This effect can certainly proceed from no other cause, than that the acid of the fat disengages itself in both these cases. Mr de Machy, an intelligent apothecary of Paris, and an able chemist and observer, has made a remark upon this subject which corresponds with this opinion; which is, that all the rancidity of fat may be taken from it by treating it with spirit of wine. Now, this evidently happens, because the spirit of wine dissolves all the portion of fat which is disengaged from its acid; that is, all the rancid part, while it does not touch that which is not changed. This practice may be advantageously employed for the preservation or recovery of some fats used in medicine, but which are rare, and not to be procured in their recent state.

One of the chief uses of fat probably is, to receive into its composition, to blunt and correct, a great part of the acids of the aliments, and which are more than are requisite to the composition of the nutritive juice, or which nature could not otherwise expel. This is certain, that the greater the quantity of aliments is taken by healthy animals above what is necessary for their nourishment and reproduction, the fatter they become. Hence animals which are castrated, which are not much exercised, or which are come to an age when the loss and production of the seminal fluid is less, and which at the same time consume much succulent aliment, generally become fatter, and sometimes exceedingly so.

Although fat be very different from truly animalised substances, and appears not easily convertible into nutritive juices, it being generally difficult of digestion, and apt to become rancid, as butter does in the stomachs of many persons; yet in certain cases it serves to the nourishment and reparation of the body. Animals certainly become lean, and live upon their fat, when they have too little food, and when they have diseases which prevent digestion and the production of the nutritive juice; and in these cases the fatter animals hold out longer than the leaner. The fat appears to be then absorbed by the vessels designed for this use, and to be transformed into nutritive juice.

the sea-language, signifies the same with broad. Thus a ship is said to have a fat quarter, if the trussing-in or tuck of her quarter be deep.

Fat is used also for several utensils; as, 1. A great wooden vessel, employed for the measuring of malt, and containing a quarter or eight bushels. 2. A large brewing vessel, used by brewers to run their wort in. 3. A leaden pan or vessel for the making of salt at Droitwich.