482 



MUCUS. 



The secretion of the Schneiderian membrane, 

 according to the analysis of Berzelius, is com- 

 posed as follows : 



Mucus 5.33 



Alcoholic extractive and alkaline lactate 0.30 

 Chlorides of potassium and sodium . . 0.56 

 Aqueous extractive, traces of albumen, 



and a phosphate 0.35 



Soda, combined with the mucus 0.09 



Water . 93.37 



100.00 



The 

 which 



chemical 

 Berzelius 



characters of the substance 

 notices in this analysis as 

 " mucus" are as follows. It is not soluble 

 in water, but swells up and becomes transpa- 

 rent. When dried it is again capable of being 

 swelled by water; but after this experiment 

 has been repeated several times it becomes 

 of a yellow colour, and assumes somewhat 

 the appearance of pus. When boiled in water 

 it neither hardens nor contracts ; but after this 

 treatment it is found, to a certain extent, to 

 have lost its property of swelling. When dry 

 it is of a yellow colour and transparent. By 

 distillation it yields carbonate of ammonia and 

 empyreumatic animal oil. The ashes obtained 

 from this substance yield phosphate and car- 

 bonate of lime, with traces of carbonate of 

 soda. This mucus is soluble in weak sulphuric 

 acid ; the strong acid darkens its colour and even- 

 tually destroys its texture. Weak nitric acid co- 

 agulates it superficially and renders it partially 

 yellow : long digestion in this acid causes 

 its solution. Acetic acid contracts it, but 

 does not dissolve it even when assisted by 

 heat. It dissolves from it, however, a portion 

 of albumen, which renders the solution preci- 

 pitable by the ferrocyanuret of potassium. 

 Caustic potash renders this mucus more tena- 

 cious, but by digestion it dissolves it. In- 

 fusion of galls coagulates it when dissolved 

 in acids or when swelled by water. These 

 characters described by Berzelius may be re- 

 ceived as the general properties of that substance 

 to which mucous secretions owe their viscous 

 character. 



Urinary mucus. This form of mucus is 

 best obtained by allowing recently voided urine 

 to remain at rest in a tall ylass vessel, when 

 the mucus will subside after some hours, and 

 may be collected by pouring off the super- 

 natant fluid as nearly as possible without 

 disturbing the precipitate, and throwing the 

 remaining part of the secretion on a filter; 

 the mucus will now be retained on the paper. 

 Its properties are as follows : when dried on 

 paper it exhibits a bright surface; on being 

 moistened, however, it rapidly assumes its 

 original appearance. It is insoluble in sul- 

 phuric acid, but the nitric and acetic acids 

 dissolve it in large proportion, and the solution 

 is precipitable by ferrocyanuret of potassa : 

 caustic potassa in solution dissolves it entirely. 



Salivary mucus. The saliva, as it passes 

 from the mouth, contains, in all probability, 

 two kinds of mucus; one derived from the 

 mucous membrane lining the mouth, and the 



other from the internal membrane of the salivary 

 ducts. When saliva is allowed to stand it 

 very soon separates into two parts ; one a 

 supernatant liquor of a slightly milky hue, 

 and the other a deposit of a white colour, 

 which in this state does not exhibit the ordinary 

 physical characteristics of mucus. On pouring 

 oft' the liquor, however, and then agitating the 

 deposit with water, it immediately assumes 

 the glairy character ; indeed, without the addi- 

 tion of water it will exhibit a mucoid tenacity 

 if an attempt be made to raise it from the 

 vessel in which it has collected. The liquor 

 which has been poured off from this dense 

 form of the principle still contains a portion 

 of mucus in suspension, which may be ob- 

 tained by dilution with water, and may pro- 

 bably be a less coherent form of mucus secreted 

 by the lining membrane of the salivary ducts. 

 These two forms of mucus have much the 

 same chemical characters, being insoluble in 

 water and coagulable, and rendered firmer, 

 by the acetic, hydrochloric, and sulphuric 

 acids. The liquors obtained by digesting these 

 acids on mucus are not precipitable by the 

 addition of alkalies, which shows that this 

 form of the secretion does not contain any 

 free subphosphate of lime. It is dissolved 

 by caustic alkalies and precipitable by the 

 acids when thus dissolved : the solution in 

 alkalies, however, is not complete, a residue 

 being always obtained, which is soluble iu 

 acid, but which cannot be precipitated from 

 the acid solution by means of caustic alkali, 

 and, therefore, is not an earthy salt. Notwith- 

 standing this, however, we can always obtain 

 evidence of the existence of phosphate of 

 lime in considerable proportion by incinerating 

 mucus ; and Berzelius considers the tartar 

 formed on the teeth to be derived from this 

 source. This form of mucus is considered 

 by Berzelius to approach very nearly to that 

 obtained from the stomach and intestines: it 

 differs greatly from nasal mucus, which is 

 soluble in the sulphuric and nitric acids. 



Intestinal mucus. The mucus of the stomach 

 and intestines can be best obtained by washing 

 the mucous surfaces of those organs taken 

 from an animal that has fasted some hours : 

 it is occasionally observed adhering to ex- 

 crement. This mucus, when dried, is no 

 longer capable of assuming ihe tenacious 

 character on being moistened with water, but, 

 according to an observation of Berzelius, re- 

 quires an alkaline solution for that purpose: 

 it is coagulable by the acids. The acetic acid 

 acts powerfully upon it, solidifying it com- 

 pletely. None of the acids dissolve it; the 

 acetic acid seems, however, to have a partial 

 action, since the liquor obtained by digesting 

 it is precipitable by the addition of infusion 

 of galls, but not always by the ferrocyanuret 

 of potassa. The caustic alkalies dissolve this 

 mucus, and the addition of acids precipitates 

 it when thus brought into solution. 



Mucus of the gall-bladderhzs been examined, 

 and appears to resemble that last described ; 

 it is insoluble in the acids and precipitable 

 In i hem from solution in alkalies. 



