FIBROUS TISSUE. 



39 



from 34^3 to ^'gj, of an inch in diameter (Harley). The fibres branch and 

 anastomose freely with one another. They are homogeneous in appearance, 

 with dark borders, and are usually seen curled up at their broken ends. They 

 remain unaltered by acetic acid. 



Each of these elements of the connective tissue is developed from cells. 

 Ivolliker describes the yellow elastic fibres as developed from the stellate 

 branching corpuscles, which may sometimes be found free in the areolar tissue, 

 and which Virchow has denominated " connective-tissue-corpuscles" (Fig. 9) ; 

 while the white fibrous tissue is formed from the coalescence of fusiform cells, 

 which elongate into fibrillse as shown by Fig. 10. 



Fig. 8. 



Fig. 9. 



Fig. 10. 



Stellate formative 

 cells of fine elastic 

 fibres, from the ten- 

 do Achillis of a new- 

 born child. (Mag- 

 nified 350 times.) 



Yellow elastic tissue. (High power.) 



Formative cells of areo- 

 lar tissue from sheep's 

 embryo. (Magnified 350 

 times.) a, Cell without 

 any indication of fibrils ; 



b, with commencing, and 



c. with distinct fibrils. 



The two tissues just described are very widely distributed in the body, espe- 

 cially the white fibrous tissue. This latter forms nearly the whole of all the 

 firm investing membranes, viz., the muscular fascise, the periosteum, the invest- 

 ments of the various glands (such as the .tunica albuginea testis, the capsule of 

 the kidney, &c.), the investing sheath of the nerves (neurilemma), and of va- 

 rious organs, as the penis, and the eye (sheath of the corpora cavernosa and 

 corpus spongiosum, sclerotic, and choroid). Into all these parts, however, the 

 elastic tissue enters in greater or less proportion. The tendons and most of 

 the ligaments are also formed almost entirely of the white fibrous tissue, but 

 with some elastic fibres intermixed. The basis of the serous and mucous mem- 

 branes is formed of connective tissue, disposed in a layer. The common sub- 

 cutaneous cellular or cellulo-adipose tissue has been taken above as the typical 

 form from which to describe connective tissue. Connective tissue also enters 

 largely into the formation of the bloodvessels, glands, and, in fact, almost every 

 organ in the body. The organs which are formed almost exclusively of the 

 yellow elastic tissue are the ligamenta subflava of the vertebrae, the elastic 



