ITS MORPHOLOGICAL CONSTITUENTS. 371 



more than a mass of strongly refracting globules, when seen in a 

 finely comminuted form, under high magnifying powers. The black, 

 sooty colour has frequently been ascribed to lamp smoke, or to 

 finely comminuted coal-dust, which has been inhaled ; but although 

 I have never been able to detect anything of the kind, I would 

 not, on that account, deny that under certain conditions, as, for 

 instance, in colliers, smiths, &c., coal-dust may become mixed with 

 the bronchial mucus. Many of the experiments instituted in 

 relation to this subject are hardly worthy of confidence. 



Free fat occurs in almost every kind of mucus, either in the 

 form of vesicles or of very minute granules, and either in mere 

 traces or in large quantities. 



Molecular or elementary granules are seldom absent from the 

 mucous juice, but they are more decidedly observable when the 

 inucus has originated in a diseased structure, as in tuberculosis 

 or cancer, but more especially in typhus, in which the milk- 

 coloured sputa appear, when seen under the microscope, to be 

 enveloped, as it were, in a veil of very fine granules. We still 

 more frequently remark the presence of such granules in intestinal 

 mucus, owing to the favorable conditions afforded for the separa- 

 tion of these molecules by the decomposition of albuminous 

 substances. 



Intestinal and cellular formations of various shape and 

 size, (Valentin's exudation-2ells,) as well as similar elements 

 from the solitary and agminated glands which are usually found 

 within the mucous membranes, are of very frequent occurrence in 

 morbidly secreted mucus. 



Vibriones, microscopic fungoid growths, and similar organic 

 particles, can only be considered as of incidental occurrence. 



Amongst the chemical constituents of the mucus, mucin occupies 

 the first place. The presence of this substance imparts to the 

 mucus its most important properties ; but, unfortunately, it has 

 never yet been completely separated from the above described 

 morphological substances, neither has it been obtained pure and 

 free from other chemical organic or inorganic matters. This may 

 be one of the causes why different mucous juices often behave 

 very differently towards individual solvents and reagents. 



Mucin is generally considered as insoluble in water, and as 

 distributing itself in a finely comminuted state through the fluid in 

 which it swells ; occasionally, however, as Scherer* has observed, 

 a mucus is found which actually dissolves in water, and may be 



* Ann. d. Ch. u. Pharm. Bd. 57, S. 196-201. 



2 B 2 



