MUCUS. 367 



Mucus. 



THERE is scarcely any animal fluid within the entire range of 

 the theory of the juices that has been so little investigated, in a 

 scientific point of view, as the mucus ; and the reasons of this are 

 sufficiently obvious. In the first place, the expression " mucus" 

 has a very vague signification ; for although the proposition has 

 been advanced, that the secretion of the mucous membranes alone 

 is to be regarded in the light of mucus, we yet find, that under 

 certain conditions there is secreted in the animal organism a limpid, 

 viscid juice, having all the characters of mucus, without however 

 being secreted from a true mucous membrane with the so-called 

 mucous follicles. We need here only refer to the mucous 

 contents of certain cysts which yield, according to the investi- 

 gations of Virchow* and Rokitansky,t all the reactions which 

 have been regarded as characteristic of normal mucus. Several 

 colloid abnormal as well as normal structures, as, for instance, 

 the gelatin of Wharton, become converted into a fluid, which 

 cannot be distinguished by any reaction from normal mucous 

 juice. Another and still more important ground for the silence of 

 chemists in reference to the constitution of mucus is, that the nor- 

 mal mucus is always so filled or interspersed with morphological 

 elements, that it cannot be obtained in a purely chemical con- 

 dition. In the present state of analysis, we are unable to separate 

 these structures from the actual mucous juice, and we cannot pro- 

 secute a satisfactory chemical investigation of this substance, except 

 in those rare cases in which a mucous juice is secreted which 

 contains few of these cells, either from their original scarcity, or 

 from the facility with which they may incidentally be removed 

 from the fluid. These cases, as we have already observed, are rare, 

 and the question even then remains, whether the substance we are 

 investigating is perfectly identical with the mucous juice. May 

 we venture, on the strength of some few coincident reactions, to 

 pronounce upon the identity of juices springing from such different 

 sources, whilst we think ourselves justified in separating globulin 

 from albumen, and vitellin from casein ? Can we re-establish, by 



* Verhandl. der Gesellsch. f. Geburtshulfe in Berlin. 1848. Bd. 3, S. 203. 

 t Zur Anatomie des Kropfes. Wien, 1849, S. 11, reprinted from first volume 

 of Denkschriften der mathem. naturwiss. Classe d. kais. Akad. d. Wissensch. 



