I have sought for the cause of this difference, and it has not appeared difficult to find it, since where injections develop few capillaries, there is only nutrition going on, as the bones, the muscles, the cartilages, the fibrous bodies, &c. are a constant proof; on the contrary, in all those in which many fluids enter, there are, besides nutrition, other functions, such as exhalation and secretion. Hence why a serous surface, almost as white as a cartilage in the living body, becomes ten times darker than it by the same fine injection; why the skin, compared to the fibrous organs, exhibits the same phenomenon; why in proportion to the arteries that enter a muscle and a gland, the latter admits much more injection than the other. These observations, which are uniform and invariable, prove that the capillary system is as much more developed in a part, as it has more functions to sustain. Observe in fine, that it is a kind of depot in which the fluids remain for a certain time, before serving for nutrition, exhalation and secretion. Where these three functions are united, it is necessary that there should be more fluids there, than where only one of them exists; hence more capillary vessels. The capillary system is not then in the organs in proportion to their size; a portion of the pleura contains more vessels than a tendon that is ten times larger. It is the nutritive substance that fills the place that these vessels do not occupy. We might, from what has just been said, divide the systems into two classes, from the development of their capillaries; place on one side the serous, the mucous, the glandular, the dermoid, the synovial, the cellular, &c.; on the other the osseous, the cartilaginous, the fibrous, the arterial, the venous, the fibro-cartilaginous, &c. The first class surpasses the second, considerably, in the number of its small vessels. Observe, also, that inflammation, different eruptions, all the affections, in which there is, as it is called, an afflux of humours to a part, are infinitely more frequent in the first than the second class, because all these affections are essentially seated in the capillary system, which is more developed in them. Asphyxia, apoplexy, and all the affections that make the black blood stagnate in the general capillary system, prove the same thing; in fact, examine the livid head of one who has died of asphyxia, or of apoplexy, you will see that it is especially in the skin and the cellular texture that the blood is arrested; that the muscles, the aponeuroses, exhibit besides the blood ordinarily found in them, only a small quantity of superabundant fluid, in comparison with what there is in the first organs. _Remarks upon Injections._