In health, each gland has a mode of sensibility nearly uniform, a mode which changes but little; thus each secreted fluid has an appearance, a consistence and a nature always nearly the same. But in diseases, a thousand causes change this mode at every instant. An hysterical paroxysm strikes the kidneys; in an instant they repulse all the principles that colour the urine, and this comes out limpid; the paroxysm passes off, the organ resumes its ordinary sensibility, and the urine returns to its usual state. The influence of the epileptic paroxysm extends to the sensibility of the salivary glands; in a moment, a thick, copious and frothy saliva, wholly different from the natural, comes from the mouth; after the paroxysm, the sympathetic storm is calmed in the gland, and the saliva returns to its ordinary state. If I may be allowed the comparison, the glands are in diseases like the atmosphere in the equinoxes. At these periods, the winds which succeed each other and incessantly change, often make rain, hail and snow succeed each other in a very short time; so the forces of the glandular life, constantly variable in diseases, make the different products of secretion vary with rapidity.
It is not only to secretion that the various alterations of the organic sensibility and the insensible contractility of the glands extend; these alterations when long continued, have an influence also upon their nutrition; they disturb the course of it; hence the changes of texture, the tumours of different kinds, the organic diseases, &c. that are so frequent in the glandular system, a system which presents the greatest field for morbid anatomy. The great number of organic diseases which it exhibits, in our dissecting rooms, compared with most of the other systems, is very striking. The glandular, the cutaneous, the mucous, the serous, the cellular systems, &c. hold the first rank in this respect. Observe also that it is in them that the organic sensibility and the insensible contractility are raised to the highest degree, because they are the only ones in which these properties are brought into action not only by nutrition, but also by various other functions that are going on in the insensible capillary system, viz. by exhalation, absorption and secretion.