Another phenomenon is also derived from the preceding character, and it is one that may be likewise considered as characteristic of the glandular system; viz. that in general it is in greater activity in winter than summer, in cold climates than in warm. In fact, heat which expands the cutaneous system increases the action of it at the expense of that of the glands, and reciprocally cold which contracts it, by preventing the constant exhalation that is going on there, forces the glandular system to supply this action. Hence why the same fluid, introduced into the economy, goes out with the urine in winter and with the sweat in summer; why, if we wish to produce an immediate discharge of urine in summer, it is necessary to suppress the perspiration by the sudden application of cold to the surface of the skin, by descending into a cellar, or some other subterraneous place; so that in summer we can, after digestion, make the product of the fluids pass off with the urine or the sweat, according to the temperature of the atmosphere in which we digest; why teas and diuretics forbid the use of each other, and why a physician who should employ them at the same time would know but little of the laws of our economy; why most of the diseases that are attended with an immoderate discharge of the secreted fluids, are almost always characterized by a diminution of the exhaled fluids; why in some seasons diseases have a greater tendency to be characterized by sweats, and in others by urinary, mucous evacuations, &c. It is to the greater degree of the vital activity of the glandular system in the winter, that must then be referred the frequency of catarrhs, diseases most of which suppose an unnatural increase of its action, the greater facility with which the kidneys are influenced by cantharides, &c. Physicians should have these considerations particularly in view in their treatment. It is necessary to act more upon the glandular system in winter, and the cutaneous in summer, because each system is as much more disposed to answer to the excitements made upon it, as it actually is in greater activity.
Fifth Character. Influence of Sex upon Glandular Life.
Is the life of the glandular system more active in man than in woman? As it respects the glands destined to digestion, the secretion of the tears, the evacuation of urine, &c. there is but little difference in the two sexes. As to genital glands, man has testicles and the prostate; woman has mammæ, so that in this respect they seem to be equal. Observe however that the influence of the first upon the economy, is much greater than that of the second. It is from the womb that go forth in woman the irradiations which correspond with those which the testicles send to all the other organs.
ARTICLE FOURTH.
DEVELOPMENT OF THE GLANDULAR SYSTEM.
I. State of this System in the Fœtus.
Though the secretions are not active in the fœtus, the glandular system is in general much developed. All the salivary glands and the pancreas are larger in proportion than afterwards; the liver is enormous; and the kidneys have a size much greater in proportion than they have in the adult. The same probably is true of the mucous glands, though I have not made any very precise researches upon this point. The form is different in many; the kidney for example is evidently uneven, whilst afterwards its surface is almost smooth. The colour is not the same; this is particularly striking in the salivary and lachrymal glands. These glands which are white in the adult, have in the fœtus an extreme redness which they lose by washing, which is not owing to the blood circulating in their vessels, though there is much of it in their vessels, but it is really inherent in their texture. This colour is never as great in the pancreas, though its texture is nearly the same. The texture of the glands is extremely soft and delicate at this age, which is the case with all the parts. They are divided and yield with great ease, and their vessels, which are large, carry into them a very great quantity of fluid.
Then they are, if we may so say, in a state corresponding with that of remission in the adult; they secrete even less fluid, though they appear however to be in constant action. In fact, all the reservoirs would be insufficient to contain their fluids, if in a given time, as much flowed from them as after birth. Is this because the black blood, which then enters their parenchyma, is unfit to furnish the materials of the secretions? This may have an influence, and I have elsewhere imagined it, from the circumstance that this blood is unable to support many other functions. But the principal reason appears to me to be, that in the fœtus the nutritive motion of composition predominates evidently over that of decomposition, which is very inconsiderable. Almost every thing which arrives in the organs remains in them and continues to furnish the materials of the rapid growth which is then taking place in the body; now, the secretions being principally destined to carry off the residue of nutrition, must then be very inactive.
Besides, digestion does not introduce into the blood any of those principles which, being useless to nutrition, must on this account go out as they entered, that is to say without making a part of our organs; such are for example most of the drinks, which only pass into the mass of blood, and go out immediately with the urine.
The glands of the fœtus are then like the brain at that age; though much developed, they remain inactive; they are in the expectation of action.