From the descriptions which I have now given I think it will be allowed that, inasmuch as the mucus which is obtained by the chemical analysis of different secretions fails to show, when subjected to tests, those agreements in reaction which must be regarded as essential to prove identity, the question as to the existence of any substance to which the name of " mucus " should be applied, as one of the proximate elementary animal bodies, should be regarded as concluded. That there is always a matter present in the secretions of mucous membranes, which possesses a gluti nous character, and to which the physical properties of the secretion are owing, is un doubtedly true; but this is quite a distinct question from whether or not this tenacious constituent be entitled to the rank of a proxi mate element : and the fact of a difference being observed in the chemical reactions of this body. as obtained from various secretions, strongly oppo'ses such an idea. In order to examine into this question I made, some time ago, at the suggestion of Dr. Bright, some chemical observations on those effused fluids which partake more or less of the mucous character,* such as the effusions which occur in ovarian dropsy, and to compare the results obtained with similarly conducted experiments on other fluids of a more purely serous character, and also with serum of blood, as it appeared probable that some point of difference might be detected to which the mucoid character could be traced, notwithstanding the total absence of any substance obtainable in a solid form and ex hibiting physical characters like those of mucus. I subjoin the examination of five fluids effused in ovarian tumours, and one of a purely serous character drawn from a case of ascites ; the serum of blood is also offered for comparison ; the separation of these fluids being carried only so far as the division into free albumen, aqueous extractive, and alcoholic extractive. These analyses were made on equal weights, or nearly so, of solid matters, obtained by evaporating each fluid, as previous observation had convinced me that the viscous character into the nature of which I was examining was quite independent of the degree of con centration of the effusions, the most tenacious generally possessing the lowest specific gravity.
P These analyses at once showed that the aqueous extractive existed in greater proportion in the tenacious fluids of ovarian cysts than in the more serous effusion of ascites and the serum of blood; but another difficulty remained to be solved, which was, that some of these viscous liquors which were less mucoid in character than others, did not indicate the cause of such difference when the examination had been extended only to the separation into the three parts above mentioned, viz. albumen, aqueous extractive, and alcoholic extractive. On incinerating the aqueous extractive, how ever, so as to ascertain the proportion of animal matter and alkaline salts contained in it, I discovered that, while those specimens which showed the mucoid character in a more marked degree contained salts and animal matter in nearly equal proportions in their aqueous extractive, those in which the mucoid character did not greatly predominate either showed a deficiency or excess of salts ; both conditions appearing more or less to interfere with the perfect development of the peculiar tenacious character of the secretion. I have now to notice the late ingenious and valuable observations of Dr. Babington, who has done more to assist this inquiry than any observer who has as yet examined into the subject. In a paper published in the fifth number of the Guy's Hospital Reports, Dr. Babington de scribed some experiments showing that various albuminous matters were capable of assuming the mucous character by mixture with the alkalies. Serum of blood, pus, milk, and white of egg were all so affected ; and the glairy mass so obtained was insoluble in water, precipitable by diacetate of lead, but not by bichloride of mercury or infusion of galls. It admitted of being washed with water till all traces of alkalinity were removed, but it still retained its mucous character. This syn thetical formation of mucus is a most important fact; and I see no reason whatever to doubt that the artificially formed viscous mass differs from that secreted by membrane. It is true
that the latter always contains microscopic globules, which of course are wanting in the artificial product ; but these globules are, I believe, in no way connected with the viscous character of mucus, hut are rather superadded to it, and frequently in very small proportion to the mass of the secretion.
The experiment of Hunter, who consolidated albumen by the addition of hydrochlorate of ammonia,as also the observations of Dr. Pearson on the action of some others of the neutral salts on pus, are confirmed by Dr. Babington in the paper to which I have alluded. The microscopic history of mucus, or lather of those organic globules which accompany the secretion, is a matter of considerable interest : before entering upon it, however, I wish to state my reasons why these globules are not, according to my belief, the cause of the viscous character of mucus. In the first place we do not observe them in sufficient numbers to autho rize such an opinion ; and, secondly, some of the most viscous forms of the secretion do not become corrugated to any perceptible degree by the addition of concentrated saline solutions, whereas, by some experiments lately made with my friend Mr. Lane, I have been satisfied that the mucus globules are so affected, and may easily be observed, under a powerful microscope, to expand or contract according as water, or strong solutions are mixed with them. The mucus globule admits, in fact, of the exudation or imbibition of fluids according to the laws of endosmose and exosmose, and were the greater part of a mass of mucus composed of these globules, we should observe it to corrugate in concentrated solutions; but such is not the case, as I have before stated, with many of the most viscous forms of mucus, while the mucus of the bladder, on the con trary, which (except in severe diseases) is one of the least coherent forms, shows a tendency to contract under such circumstances, and on microscopic examination proves to contain globules in large number in proportion to its mass. This reaction, I think, renders it very probable that the view I have mentioned is the correct one. Most forms of mucus swell when moistened by water or weak solutions ; but this is no proof of action on organic globules unless the opposite experiment (contraction by strong solutions) can be successfully performed. The mucus globule varies greatly, as seen in different secretions; so much so that any one who has examined this subject microscopically must be familiar with a form of globule peculiar to each secretion. I shall first describe the globule generally, and then proceed to notice its varieties in appearance. The mucus globule is nearly transparent, and larger than the blood globule. As it exists in the saliva and urine it is of a very regularly circular form, with a well defined margin and a somewhat granular surface. In the more adhesive forms of ex pectoration, however, it loses this well defined and rounded form, and its translucence is impaired ; the granular surface can always, however, be seen. In a portion of mucus taken from the back of the throat I lately had an opportunity of examining this last mentioned condition, and took occasion to examine whether or not it depended on a partially empty condition of the globule, which could be remedied by the addition of water. I found, by careful treatment, in this way under the microscope, that the bodies gradually assumed a more rounded form, and eventually exhibited an appearance almost identical with the more transparent globules observed in the saliva and urine. By sub sequently adding a concentrated solution of sugar to them, however, the original appearance was speedily reinduced, owing to the endos modic action of the situp. This experiment has led me to a belief that the cause of difference in the microscopic appearance of the mucus globule, as seen in different secretions, is attributable rather to the circumstances under which it is placed than to any difference in organization.