SEROUS AND SYNOVIAL MEMBRANES. 



515 



brane of little more than their own breadth ; 

 this membrane was prolonged at their oppo- 

 site poles into ribbon- shaped processes, of 

 excessive tenuity and considerable length. 

 Such a description greatly approximates to 

 that given by Mr. Goodsir*, of the torn-up 

 " germinal membrane " of the serous tissues ; 

 but I have not studied these objects sufficiently 

 to be able to affirm or deny the complete ap- 

 plicability of his description to them. In the 

 instance where I saw it, I rather inclined to 

 consider it a distortion and elongation of the 

 ordinary epithelia, due to accidental mecha- 

 nical violence, inflicted during the examination 

 of the specimen. 



The characters of the cells. The different 

 individual cells which may be found floating 

 in the field of the microscope exhibit great 

 diversities of appearance, so as to offer almost 

 every gradation of cell-growth. The first 

 form visible (fig. 396. ) is that of a delicate 

 pale, flat, cytoblast, which is either unaffected 

 by the application of acetic acid, or is even 

 rendered somewhat more transparent by it. 

 The next gradation (b) is still a cytoblast, 

 i.e. uncomplicated by the addition of an outer 

 cell-wall ; but dilute acetic acid renders it 

 yellowish, and much more distinct. In the 

 next variety (the next stage of development, 

 I think it may safely be termed), two outlines 



Epithelium of the Subcutaneous Bur SOB. (Magnified 

 320 .diameters.} 



are visible (c), one of the nucleus or cyto- 

 blast, another of a cell-wall exterior to this ; 

 and the distance between the two gradually 

 increases in different individuals by an in- 

 crease in the size of the cell, which, however, 

 retains its flattened oval shape. Its contents 

 are either transparent, or very faintly gra- 

 nular : and the succeeding modification mainly 

 consists in the increased granularity of the 

 contents of the cell, and in the assumption of 

 a more or less polygonal outline. This is seen 

 in the figures marked d, e,f, g ; and these 

 diagrams also illustrate another detail, viz. 

 that the polygon is anything but a regular one, 

 offering a variety of forms, some of which ap- 

 proximate to a triangle, others to a trapezium 

 or a pentagon. And though sometimes (as in 

 those marked e), they may be seen apposed 

 in groups of two or even three, yet it will be 

 recollected that many of these forms are phy- 

 sically insusceptible of the neat tesselated 

 adaptation which is seen in the hexagonal cells 



* Anatomical and Pathological Observations, 

 p. 41. 



of serous membrane. The wall of the cell is 

 still soluble in acetic acid, and the outline of 

 the nucleus is darkened by its application as 

 usual. The subsequent alterations consist in 

 a gradually increasing flattening and widening, 

 both of the cell and nucleus, but especially of 

 the former, which finally more than doubles 

 the diameter of the polygonal cell, and at the 

 same time reduces its depth to a mere scale. 

 The granular or mottled appearance of the 

 contents before spoken of now reaches its 

 maximum, often forming yellow refractile dots 

 or beads, which appear to be incompletely 

 fluid (h). The nucleus, during this process 

 of flattening, becomes somewhat larger, and 

 much less distinct; and in the larger and 

 more mottled scales, it completely disappears, 

 an effect which might at first be supposed due 

 to the obscuring of its outline by the granular 

 contents, but which is evidently independent 

 of this cause. A further difference is pre- 

 sented by the action of acetic acid, which 

 fails to affect these broad squamous epithelia 

 in any perceptible degree. 



The arrangement of the cells. Hitherto we 

 have merely enumerated and distinguished the 

 different forms of cell growth which may be 

 detected after tearing up casual portions of 

 the tissues lining the cavity : we have next to 

 determine the relative quantities of the differ- 

 ent varieties, and to specify their arrangement, 

 both with respect to each other and to the 

 surface which they clothe. 



The forms which appear greatly to pre- 

 dominate in quantity, are those represented 

 in the figure as c y d,f. Some of these are 

 nucleated cells of a flattened oval shape, and 

 others are probably similar cells, in a stage 

 immediately subsequent to the preceding, 

 when the oval vesicle becomes more or less an- 

 gular by the lateral pressure of its neighbours 

 opposing its own inherent expansion ; or, re- 

 garding a number of such bodies, when a si- 

 multaneous expansion obliges their yielding 

 walls to adopt that shape which presents the 

 fewest interstices, and thus allows of the 

 greatest amount of mean area. Were the 

 process conducted with mathematical accu- 

 racy, this shape would obviously be a hexagon, 

 and in the serous membranes it will be 

 seen with how few exceptions the cells ap- 

 proximate to that form ; but in the outline 

 of these bursal epithelia, as has been already 

 seen, the oval or circle glides into the polygon 

 by many gradations. 



Generally speaking, there is but one layer 

 of cells, and these are usually more or less 

 polygonal ; but not unfrequently a few oval 

 ones are seen in close proximity to each other, 

 and only distinguishable by the smaller dis- 

 tance between their nuclei, and the occasional 

 overlapping of their curved borders. 



The chief exceptions to the unity of the 

 layer are twofold, one at each extremity of 

 the cell-life, so to speak. For instance, pale 

 flat cytoblasts (a), in sparing quantity, some- 

 times underlie the stratum ; while, on the 

 other hand, it is often covered by the very 

 large polygonal squames(^). In either case, 



L L 2 



