The physiological question of the formation of fat, has been fully discussed within the past ten years, and it has been proven by diet and analysis, that herbivorous animals possess more fat than is taken in their food; but whether the fat be formed wholly from non-nitrogenized or from nitrogenized bodies, or partially from both, is yet undecided. Pathological considerations from the fatty degeneration of several of the organs, where the fat is found both within and without the cell,[5] appear likewise to have divided scientific men as to its origin, whether from a change of the proteine compounds of the organs, or from an abnormal plastic activity. The connexion of the organs of generation with the deposit of fat, and the increase of the latter after castration, is worthy of consideration; for the cutting off the supply of the highly albuminous semen, gives an impulse to the fat formation. The flesh and the fat of the body stand in an intimate relation to each other, and neither the non-nitrogenized nor the nitrogenized diet exclusively is conducive to health. _Repose_ is necessary, (with a proper diet,) to the formation of fat, and as the activity of the muscles requires their reparation from the food, perhaps it is as much this wearing away by activity, that hinders the formation of fat, as the increased combustion by the quickened respiration. It therefore appears to me probable that both classes of food conduce to the fat formation. It was thought that the study of adipocire would throw some light upon the question, whether fat be formed from proteine compounds, and I was surprised to find the great difference of opinion as to the formation and nature of this body, and in general, as to the changes that bodies undergo in grave yards. These various changes are ascribed by undertakers to the nature of the soil, to its dryness or moisture; but in a late removal of a grave yard in this city, some bodies were found converted into adipocire, the graves of which were contiguous to those in which decomposition had advanced to its full extent, leaving nothing but the skeleton. The preservation of some bodies seems inexplicable, according to our present knowledge, of which I may cite the well known case of General Washington, (who was not embalmed,) who having reposed in his tomb for more than forty years, was so perfectly preserved, as to have been recognised from the resemblance of his portraits. The problems proposed for this research were:— 1st. The chemical examination of different kinds of adipocire. 2d. To watch the decomposition of flesh with water, and imitating the condition of a body in moist ground. With regard to the first of these, I possessed the following specimens of adipocire: (_a_) Two from sheep buried at the country seat of the late J. P. Wetherill. (_b_) Two from human subjects, which I obtained myself from a grave yard. (_c_) From a fossil ox, presented by Prof. Leidy. (_a_) SHEEP ADIPOCIRE.