All the systems that remain to be examined are then much more insulated, perform a much less extensive part than those of which we have been treating. Confined to certain apparatus, they are unknown to the others, and have an independent life of their own, whereas the primitive systems everywhere mingle their vitality with that of the other organs, into whose composition they enter; most of them have a kind of existence and external forms which distinguish them from these last. The different parts which compose each, are almost always insulated, not connected with each other; the bones, the muscles of animal and organic life, the cartilages, the fibro-cartilages, the medullary organs, the glands, the serous membranes, the hair, &c. exhibit this insulation in a remarkable manner. Each portion belonging to these different systems, has always between it and the other portions of the same system many intermediate organs, which are of a very different nature, and which consequently belong to other systems. There are hardly any except the cutaneous, fibrous and mucous systems, which are everywhere continuous in their different parts; yet this last has no communication between that portion of it which is spread upon the digestive and respiratory apparatus, and that which belongs to the urinary and genital organs. We have seen on the contrary that the primitive systems are everywhere continuous, having no interruptions in them. The cellular, the arterial, the venous, the absorbent, the nervous are so arranged, that if it were possible to remove all the organs they enter, and leave them alone, they would form a complete whole, formed differently according to the different systems. The exhalants can also be considered as everywhere connected, as we have seen. Suppose on the contrary that the organs intermediate to the bones, the cartilages, the fibro-cartilages, &c. should be removed, all the parts of these systems would immediately be separated, and you would not have one continuous whole. The order to be followed in the examination of these systems is of no importance; we shall place them in the following order, which will comprehend 1st, the osseous; 2d, medullary; 3d, cartilaginous; 4th, fibrous; 5th, fibro-cartilaginous; 6th, animal muscular; 7th, organic muscular; 8th, mucous; 9th, serous; 10th, glandular; 11th, cutaneous; 12th, epidermoid; 13th, and finally, the system of the hair.