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SECT.  XXVI.

OF THE CAPILLARY GLANDS AND MEMBRANES.

I. 1. The capillary vessels are glands. 2. Their excretory ducts.  Experiments on the mucus of the intestines, abdomen, cellular membrane, and on the humours of the eye. 3. Scurf on the head, cough, catarrh, diarrhoea, gonorrhoea. 4. Rheumatism.  Gout.  Leprosy. II. 1. The most minute membranes are unorganized. 2. Larger membranes are composed of the ducts of the capillaries, and the mouths of the absorbents. 3. Mucilaginous fluid is secreted on their surfaces. III. Three kinds of rheumatism.

I. 1.  The capillary-vessels are like all the other glands except the absorbent system, inasmuch as they receive blood from the arteries, separate a fluid from it, and return the remainder by the veins.

2.  This series of glands is of the most extensive use, as their excretory ducts open on the whole external skin forming its perspirative pores, and on the internal surfaces of every cavity of the body.  Their secretion on the skin is termed insensible perspiration, which in health is in part reabsorbed by the mouths of the lymphatics, and in part evaporated in the air; the secretion on the membranes, which line the larger cavities of the body, which have external openings, as the mouth and intestinal canal, is termed mucus, but is not however coagulable by heat; and the secretion on the membranes of those cavities of the body, which have no external openings, is called lymph or water, as in the cavities of the cellular membrane, and of the abdomen; this lymph however is coagulable by the heat of boiling water.  Some mucus nearly as viscid as the white of egg, which was discharged by stool, did not coagulate, though I evaporated it to one fourth of the quantity, nor did the aqueous and vitreous humours of a sheep’s eye coagulate by the like experiment:  but the serosity from an anasarcous leg, and that from the abdomen of a dropsical person, and the crystalline humour of a sheep’s eye, coagulated in the same heat.

3.  When any of these capillary glands are stimulated into greater irritative actions, than is natural, they secrete a more copious material; and as the mouths of the absorbent system, which open in their vicinity, are at the same time stimulated into greater action, the thinner and more saline part of the secreted fluid is taken up again; and the remainder is not only more copious but also more viscid than natural.  This is more or less troublesome or noxious according to the importance of the functions of the part affected:  on the skin and bronchiae, where this secretion ought naturally to evaporate, it becomes so viscid as to adhere to the membrane; on the tongue it forms a pellicle, which can with difficulty be scraped off; produces the scurf on the heads of many people; and the mucus, which is spit up by others in coughing.  On the nostrils and fauces, when the secretion of these capillary glands is increased, it is termed simple catarrh; when in the intestines, a mucous diarrhoea; and in the urethra, or vagina, it has the name of gonorrhoea, or fluor albus.