CONNECTIVE TISSUES EPITHELIUM. 



Lortet of Lyons, however, as well as MM. Coruil and Ranvier, objected that 

 the leucocytes observed might have penetrated by virtue of their amoeboid 

 movements from without ; to which Ouimus replied by making experiments 

 with very resistant membranes, as with parchment paper, when he found 

 that leucocytes still made their appearance. It is to be observed that in one 

 case where cells appear to arise de novo in a blastema, namely, in the fluid 

 poured out upon the surface of a wound, 1 late experiments 2 have rendered it 

 probable that such cells really take origin from the budding of the cells at 

 the borders of the wound. Various forms of cells will be described when 

 the subjects of the skin, the alimentary, respiratory, and genito-urinary mu- 

 cous tracts, the nerves, muscles, and glandular organs are under considera- 

 tion ; and it will be advantageous to consider here the principal forms which 

 occur in a free state, and are collectively known as Epithelial and Epider- 

 moid structures, and the following sections will be devoted to the description 

 of those textures which result from the metamorphosis of cells, and are now 

 generally included under the title of Connective Tissues, embracing: 1. 

 Areolar, fibrous, tendinous, and ligamentous tissues ; 2. Elastic tissue ; 3. 

 Fat; and 4. Cartilage and Bone. These tissues all present the features in 

 common of originating in cells, of presenting a low type of organization, of 

 possessing an indifferent supply of bloodvessels and nerves, of being easily 

 repaired when injured, whilst they frequently present forms that are inter- 

 mediate to one another, and finally, as their name implies, they all subserve 

 the purpose of connecting or supporting the other textures of which the 

 body is composed. 



EPITHELIUM. The skin, mucous and serous membranes, the interior of 

 the vessels, and of the ducts of many glands, are covered with one or more 

 layers of cells, which give to these parts a smooth and uniform surface, and 

 enable them to supply, by structures capable of easy renewal, the losses 

 they experience from the friction to which they are constantly subject. The 

 innermost recesses of glandular organs are also lined by cells, the function 

 of which appears to be the separation from the blood, or the formation from 

 the materials supplied by that fluid, of the secretion proper to each. Four 

 principal kinds of cells have been distinguished by microscopists, forming, 



by their juxtaposition, tessellated 

 or pavement, cylindrical or colum- 

 nar, spheroidal or glandular, and 

 ciliated epithelium, and the con- 

 tours of the cells may be brought 

 into view by immersing the fresh 

 membrane for a few minutes in a 

 one-half or one-quarter per cent, 

 solution of nitrate of silver, and 

 then washing in distilled water. 

 The first-named form is found as 

 a single layer of flattened cells in 

 the interior of the vessels and 

 synovial and serous membranes 

 surface (Fig. 14). The cells are there 

 seen to be flat, and are often either 



FIG. 14. 



mil the 



of centrum tcndimmi <>f mi. hit, strongly colon d 



nitrate <>f silver; a, <hirk silver lines of the inter- s j nuous j n out line, or are rendered 



stitial substance Of the enilothelial eelN; />, cell-sill.- i , I K 1 



stance; ,, nuelens. - * 



lary lymphatic. 



The smaMer ee,N |i, over a ea,,il- 



P 



_ 



They possess a cell-wall, and a 



1 SIT Arnold, Virchow'.- Archiv, Band xlvi. 



'* See Ehertli and Hotl'mann, Virchow's Archiv, Band li. 



