54 HORNY TISSUE, 



The questions to which the present condition of histological 

 inquiry leads the chemist in his examination of the horny tissues, 

 are briefly these : Is there a substance which holds together the 

 cells of these tissues, agglutinating them to a certain extent, and, if 

 so, what are the chemical properties and the composition of this 

 substance ? What is the chemical character of the morphological 

 constituents of these dried cells or vesicles of the horny tissue ? 

 What is the nature of the cell-membrane, and of the nuclei 

 which exist in almost all of the cells, and finally, of what do the 

 generally dried contents of these cells consist ? Are the morpho- 

 logical elements identical in different kinds of horny tissue, or do 

 they often differ essentially from one another, as various reactions 

 would seem to indicate ? What is the constitution of these 

 morphological elements in the newly forming or just formed cells 

 in the vicinity of the rete mucosum of the skin or the mucous 

 layer of the nails ? What metamorphoses do analogous elements 

 undergo during the gradual drying and the alterations in form of 

 the originally filled spherical or oval cells ? 



It unfortunately happens that the chemical investigations 

 hitherto instituted on this subject have contributed rather to the 

 suggesting than to the answering of these questions ; for although 

 chemical reagents have enabled us duly to examine the morpho- 

 logical elements of the horny tissue, chemistry is still wholly 

 incompetent to indicate the position which, from its form, each 

 structure ought to occupy in the series of organic atomic groups. 

 We should consider it a great step in advance, if we knew how to 

 isolate any one of the morphological constituents of the horny 

 tissue, in the same manner as we can isolate elastic fibre by 

 chemical means from the yellow ligaments or the middle coat of 

 the arteries. The different horny tissues have hitherto been 

 regarded by chemists simply as homogeneous bodies, and analysed 

 as such, after they had been freed by indifferent solvents from fat, 

 salts, and the so-called extractive matters. Although these kinds 

 of analysis have most frequently been conducted under Mulder's 

 superintendence, no one is more thoroughly convinced than Mulder 

 himself of their insufficiency in respect both to the histological and 

 chemical knowledge of these tissues. 



We abstain from entering more minutely into the consideration 

 of the internal structure of the different horny tissues, as the obser- 

 vations already made on this subject will sufficiently explain the 

 state of our chemical knowledge of these structures. The micro- 

 chemical reagents to which we are now about to refer, afford, as we 



