378 MUCUS. 



and their conversion into a mucous fluid. Such a conversion of cells 

 into a mucous substance would, therefore, at all events not be wholly 

 without analogy. Scherer and Virchow, however, go still further, 

 and advance the opinion, based upon several pathologico-histological 

 observations and chemical experiments, that certain colloid sub- 

 stances, and others adapted for the formation, of urine, may be 

 converted into mucus under certain conditions which still remain 

 to be explained, and even without any cell-formation ; and hence 

 they regard the latter mode of development as associated with the 

 existence of colloid or cartilaginous substances. This view is 

 supported not only by the absence of epithelial structures 

 in many mucus-containing cysts, but more especially by the 

 frequently noticed conversion of the gelatin of Wharton into 

 perfect mucus. It appears to us still to require accurate chemical 

 experiments, to decide which of these two hypotheses deserves 

 the preference. The elementary analyses which were made by 

 Scherer on a single variety of mucous juice, unfortunately do not 

 enable us to decide the question, both because the atomic weight 

 could not be determined, and because we are still entirely deficient 

 in an accurate analysis of the epithelial cells, the colloid substance, 

 &c. It remains for us to hope that the investigating powers of 

 men like Scherer may before long enrich science with the know- 

 ledge necessary for elucidating a subject which is so intimately 

 associated with the advancement of physiology. 



The localities in which mucus occurs clearly demonstrate 

 that it is especially designed to serve as a protecting medium to 

 all the parts which are placed in a reciprocal connection with the 

 outer world (Joh. Miiller)* 



CUTANEOUS SECRETIONS. 



ALTHOUGH in a certain point of view we may regard the 

 epidermis, the nails, hairs, feathers, and scales, as products of the 

 secretion of the skin, these objects will find a more appropriate 

 place in the third volume, when we treat of histological chemistry. 

 We shall, therefore, here only notice those two well-known secre- 

 tions, the sebaceous matter and the sweat. 



The sebaceous matter is secreted by those innumerable glandu- 

 lar structures, the folliculi sebacei, which are distributed over the 



