Very different ideas have been entertained of the nature of these villi; they have been considered in the stomach and the œsophagus as destined to the exhalation of the gastric juice, in the intestines as serving for the absorption of chyle, &c. But, 1st, it is difficult to conceive how an organ everywhere nearly similar, can perform in different parts functions so different; I say nearly similar, for we shall see that these papillæ exhibit differences of length, size, &c. without having any of texture or structure. 2d. What can be the functions of the villi of the pituitary membrane, of the internal coat of the urethra, the bladder, &c. if they have not relation to the sensibility of these membranes? 3d. The microscopical experiments of Leiberkuhn upon the vesicle of the intestinal villi have been contradicted by those of Hunter, of Cruikshank and especially of Hewson. I am certain that I have never seen any thing similar on the surface of the small intestines, at the time of chylous absorption; and yet it would appear that a thing of inspection could not vary. 4th. It is true that these intestinal villi are everywhere accompanied by a vascular net-work, which gives them a red colour very different from the colour of the cutaneous papillæ; but the non-appearance of the cutaneous net-work is owing to the pressure of the atmospheric air, and especially to the contraction which it occasions in the small vessels. Observe in fact the fœtus as it comes from the womb of its mother; its skin is as red as the mucous membranes, and if its papillæ were a little longer, it would resemble almost exactly the internal surface of the intestines. Who does not know moreover, that the vascular net-work surrounding the cutaneous papillæ, is rendered evident by fine injections, so as to change their colour entirely? That in the stomach this vascular net-work continuous with the exhalants furnishes the gastric juice, and that in the intestines it intermixes with the origin of the absorbents, so that these embrace the villi, we cannot doubt after the experiments and observations of anatomists who have recently engaged themselves in investigating the lymphatic system. But this does not prevent the base of these villi from being nervous, and them from performing upon the mucous membranes the same functions that the papillæ do upon the cutaneous organ. This manner of regarding them by explaining their existence generally observed upon all the mucous surfaces, appears to me to be much more conformable to the plan of nature, than to suppose them in each place with different and often opposite functions.