484 



MUCOUS MEMBRANE. 



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 ihe^e 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 lo them, however, the original appearance 

 was speedily reinduced, owing to the endos- 

 modic action of the sirop. 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. 



It would appear, from the facts collected 

 up to the present moment on this subject, that 

 \ve are justified in considering, 1st, that mucus 



is a compound of albumen in a state of close 

 combination with alkaline salts, and probably 

 free alkali ; 2nd, that the artificial compound 

 formed by the addition of alkalies and neutral 

 salts to albuminous matter is essentially the 

 same as mucus; 3rd, that the mucus globule 

 is superadded to the viscous matter in the 

 secretions of mucous membranes, and is in 

 no way concerned in imparting the peculiar 

 tenacious character to such fluids. 



A great deal of trouble has been taken to 

 devise chemical means of distinguishing be- 

 tween pus and mucus, or to detect the presence 

 of the former when existing combined in 

 small proportion with the latter. No chemical 

 method of inquiry can ever be applicable to 

 this question : the microscope must be had 

 recourse to for the detection of the pus globule, 

 if the mucus be suspected to contain it in 

 quantity so small as to escape casual exami- 

 nation. When pus is present, however, even 

 in very small proportion to the mucus, its 

 physical characters are so distinct that no 

 chemical or microscopical tests can possibly 

 be required. Considered as a means of proof, 

 the folly of using chemical tests is at once 

 apparent when we recollect that the question 

 as regards pus is entirely one of structure, 

 and we cannot in reason use chemical tests 

 to determine the presence or absence of a 

 globule. When pus exists as a deposit in 

 urine, we may easily distinguish it from the 

 phosphates with which it is sometimes con- 

 founded by adding an alkali, as recommended 

 by Dr. Babington, in which case the deposit 

 (which must be previously separated by de- 

 cantation from the urine) assumes the glairy 

 character of mucus, and thus shows its albu- 

 minous nature. As affording us a distinctive 

 test, therefore, between these two substances, 

 chemistry becomes useful ; but inasmuch as 

 the addition of alkali to most forms of albu- 

 minous matter developes a mucous tenacity, 

 the re-agent cannot correctly be called a test 

 for pus. We become assured of the presence 

 of pus by this reaction only, because previous 

 experiment has shown that the phosphates 

 and pus are the only two substances assuming 

 a peculiar and similar appearance in the urine. 



( G. Owen Rees.) 



MUCOUS MEMBRANE. This term has 

 been usually and properly restricted to those 

 large expansions of membrane, in the interior 

 of the body, which are continuous with the 

 external tegument : but it is impossible, in the 

 present state of knowledge, to treat of these 

 apart from the true glands and the skin, which 

 form with them a great system, to which the 

 generic term mucous will be applied in this 

 article. 



Many anatomists since the time of Bonn* 

 have treated of the mucous membranes and 

 skin under the common title of tegumentary 

 membranes ; and the opinion has been gradu- 



* Bonn, Specimen Anatomico-Medicum Inaug. 

 &c. de continuationibus membranarum, &c. in San- 

 diforti Thesauro, torn. ii. p. 265. Roterod. 1769. 



