There are many synovial membranes the existence of which is variable; such as, for example, that of the great glutæus, in the place of which there is often found only a cellular mass. These membranes are in general very dry when they exist. Synovia can scarcely be discovered in them. They resemble in this respect the articular synovial membranes of the vertebræ, the clavicle, &c.
This system, one of the most important in the animal economy, differs from most others in this, that the texture which is peculiar to it is not precisely the same in all the organs that compose it. The fibres of a muscle of animal life would as well serve for the structure of any other muscle of the same system. The tendinous fibres, the cartilaginous, osseous textures, &c. are everywhere the same. On the contrary, the texture of the liver would not serve to compose the kidney, nor that of this last the salivary glands. The glandular system then has a resemblance in its different parts only by certain general attributes which have many exceptions.
Authors have given the name of glands to organs to which it does not belong; such as the thyroid, the pineal, the lymphatic glands, those especially that are in the neighbourhood of the bronchia, the thymus, the suprarenal, &c. We should call by this name only a body from which flows, by one or many ducts, a fluid which this body separates from the blood which it receives by the vessels that go to it. 1st. On the head, the salivary, the lachrymal, the Meibomian and the ceruminous glands of the ear, and the amygdalæ.; 2d, the mammæ on the thorax; 3d, in the abdomen, the liver, the pancreas and the kidneys; 4th, in the pelvis, the prostate and the testicles; 5th, on the whole trunk and the face, the very numerous collection of mucous glands; these are nearly all that are dependant upon the glandular system; all the other organs which belong to it by this name, are foreign to it in their texture, their properties, their life and their functions. In this point of view, the division of Vicq d’Azyr is inaccurate.
The extremities contain nothing which belong to this system, no doubt because the fluids which it separates almost all serve for the functions of organic life, whilst in the extremities every thing is in relation to animal functions.