WHITE FIBROUS TISSUE. 51 



From a freshly slaughtered ox, sheep, or pig (the first being the 

 best) obtain a piece of the spinal marrow from the region of the neck. 

 Out it transversely into discs about one-eighth of an inch thick, and 

 place them in the chromic-acid fluid diluted with an equal bulk of 

 water. After thirty-six hours, place one of the pieces in water, and 

 with a needle pick out minute fragments from the anterior horn of 

 the gray matter (refer to the diagram of the spinal cord) and trans- 

 fer them to a slide. Add a drop of water and break the tissue into 

 minute fragments by teasing with a pair of needles. Examine from 

 time to time with L. to note the progress of the teasing. When 

 properly teased, put on the cover-glass and search for large nucleated 

 cells from which the prolongations or horns are given off. Compare 

 with Fig. 123. 



Cells may be classified as follows: 



Epithelial covering-cells, as in skin. 



Endothelial lining-cells, lining vessels or cavities, n' 



Glandular constituting the parenchyma of organs. \ 





CONNECTIVE (FIBROUS) TISSUES. 



Certain elementary structures of similar origin and mode of de- 

 velopment, and serving alike to unite the various parts of the body, 

 have been termed connective tissues. Custom has restricted the 

 term, in its every-day employment, so as to apply to white fibrous 

 tissue or, at least, to tissue which always resembles this more closely 

 than any other, and I shall so use the expression in this work. 



WHITE FIBROUS TISSUE. 



This, the connective tissue par excellence, is composed of exceed- 

 ingly fine fibrillae (one-fifty thousandth of an inch), which are aggre- 

 gated in irregularly sized and variously disposed bundles. It forms 

 long and exceedingly strong tendons connecting muscle and bone; 

 its fibres interlace, forming the delicate network of areolar tissue ; it 

 forms thin sheets of protecting and connecting aponeuroses; or, sup- 

 porting vessels, it permeates organs, and sustains the parenchyma of 

 glands. 



The fibres are held together by means of a transparent cement, 

 which may be softened or dissolved in acetic acid. They may exist, 

 as in dense tendons, without admixture. 



Cells are found between the bundles of fibres, known as connective- 

 tissue corpuscles or fibro-blasts. The older and more dense the struc- 

 ture, the less frequent are these cells ; while in young (recent) con- 



