BY DR. KLEIN. - 41 



scalpel, we meet with cells corresponding to the deepest layers, 

 which possess more of a cylindrical form, and contain' an 

 oblong nucleus. Similar results may be obtained if we mace- 

 rate a portion of the mucous membrane in bichromate of pot- 

 ash solution. 



To study the epithelium of the cornea in the fresh condition 

 we proceed in a somewhat similar way. A frog is held by an 

 assistant, its nictitating membrane drawn down, and from the 

 anterior corneal surface a thin layer is scraped with a lancet- 

 shaped, or a cataract knife ; the fragment removed is then 

 broken up and covered in aqueous humor, or in half per cent, 

 solution of common salt. Here we find not only isolated cells, 

 but connected masses of epithelium arranged in layers. ]>y 

 means of the fine adjustment the individual cells of these layers 

 may be studied; but we shall not at present occupy ourselves 

 further either with the epithelium of the anterior corneal sur- 

 face, or with the membrana Descemeti, since they will be fully 

 described when we treat of the cornea. 



The epithelium of the skin (epidermis), and especiall}" of the 

 elements of the stratum corneum, \n&y be readily brought under 

 investigation as follows : A small shred is raised from cither 

 the back, or palm of the hand, and covered in water ; reagents 

 which act upon horny structures, as, e.g., dilute and concentrated 

 acids and alkalies, may then be added. For the stiuty of the 

 cells of the Rete Malpighii, or portion of the epidermis which 

 lies upon the corium, or true skin, the pointed condylomata so 

 frequently met with, are peculiarly suitable. Cancroid tumors 

 are equally to be recommended. We place these structures in a 

 sherry-colored solution of bichromate of potash, and let them 

 macerate tuere for several days. At the end of this time we 

 scrape off a small portion of the epithelium with a scalpel, 

 transfer it to a drop of water or bichromate solution on a slide, 

 break it up with a needle-handle, and apply the cover-glass as 

 usual. In such preparations we meet with very striking forms 

 of the so-called ridged cells, i.e., polyhedric cells whose surfaces 

 are covered with ridges and intermediate furrows, and whose 

 borders therefore, when seen in profile, appear as if serrated. 

 Wherever t-o such surfaces are applied to each other, the 

 ridges of the one fit into the furrows of the other, the line of 

 adaptation being a zigzag one. The granular protoplasm of 

 the individual cells, the sharply-bordered, ovoid, single or double 

 nuclei, which sometimes lie in avacuole in the protoplasm, and 

 the nucleoli are clearly seen. Very interesting are the nume- 

 rous cells in various stages of division. These are represented 

 by the following forms: 1. Ceils containing a single nucleus 

 constricted into an hour-glass shape, with two nucleoli. 2. 

 Cells which possess two nuclei lying quite close to each other, 

 each with a nucleolus. 3. Cells with two nuclei lying at a 



