

CONNECTIVE TISSUE. 



149 



of reticular tissue no doubt a single plastid has become basis- 

 substance, but here two or more plastids must have coalesced 

 in order to produce a nucleated field of basis-substance the 

 first evidence of a territory. Formations of both these varie- 

 ties, however, may occur in one and the same specimen. (See 

 Fig. 50.) 



FIG. 49. RETICULAR MYXOMATOUS TISSUE OF A VILLUS OF THE 

 PLACENTA OF A HUMAN EMBRYO, FOUR MONTHS OLD. 



EE, epithelial cover of thevillus; B, solid bud of a growing villus; CO, capillary blood- 

 vessels, overlapped by the myxomatous reticulum. Magnified 500 diameters. 



The lymph-ganglia, including the thymus of embryos and the 

 spleen during the whole of life, exhibit the reticular myxomatous 

 structure in a marked manner. (See Fig. 31.) The reticulum is 

 either fibrous or composed of nucleated branching plastids,* while 

 the meshes, varying greatly in size, contain plastids, either single 

 or in groups, in all stages of development : the lymph-corpuscles. 

 Of this variety of lymph-tissue the substance of the thyroid body 

 may perhaps consist, although the spaces holding the lymph- 



* C. Toldt has demonstrated that in the thymus of low vertebrates (frog, 

 newt) the reticulum retains its protoplasmic character for life. Lehrbuch 

 der Gewebelehre, 1877. 



