58 



CONNECTIVE TISSUE CARTILAGE BONE 



Under these conditions they are no longer straight, but present a grace- 

 fully curved contour. The elastic fibers also possess a glassy, shining, or 

 highly refractive appearance, the collagenous fibers by comparison look- 

 ing dull and opaque. 



Elastic fibers stain but slightly with most dyes; they are readily 

 colored by orcein and by WeigertV elastic tissue stain (resorcin-fuchsin), 

 both of which serve as specific dyes for these 

 fibers, coloring the fibers dark brown or 

 black. Elastic fibers are not dissolved by 

 dilute acids or alkalies even when boiled, and 

 are only digested by artificial gastric juice 

 after a lapse of several hours ; they are, how- 

 ever, readily digested in faintly alkaline solu- 

 tions of pancreatin. They consist of the al- 

 buminoid body, elastin, which on boiling does 

 not yield gelatin. Both collagenous and elas- 

 tic fibers arise by a similar process involving 

 transformation of the exoplasm of their re- 

 spective fibroblast progenitors into a fibrillar 



FIG. 65. LONGITUDINAL SECTION OF TENDON OF 

 HUMAN FINGER. 



Only the nuclei of the tendon cells are conspicu- 

 ous, scattered in rows among the collagenous fibrils. 

 The rows of nuclei mark the boundaries of the 

 primary bundles. X 750. 



FIG. 66. PORTION OF 

 TENDON FROM A Cow. 



conn. t. c., connective tis- 

 sue cells (tendon cells) seen 

 from the side and, in one case, 

 from the surface. (From 

 Dahlgren and Kepner's "Ani- 

 mal Histology," Macmillan 

 Co.) 



structure. Whether the fibers are deposited as such or arise by coales- 

 cence of more fundamental granular elements is a disputed point. 



The cells of areolar tissue are few in number, but may include any 

 of the several varieties, though lamellar and spindle cells together with 

 leukocytes form the more common types. Many of the lamellar cells are 



