148 



CONNECTIVE TISSUE. 



either plastids or fibers, with nuclei at their points of intersec- 

 tion, inclosing a jelly-like basis-substance. The center of a field 

 of basis-substance often contains a nucleus, which indicates that 

 the field has originated from a plastid, the peripheral portion of 

 which, by a chemical change of its liquid, was transformed into 

 basis-substance, while the nucleus remained unchanged. 



The placenta is, to a great extent, composed of this tissue, 

 the reticulum being of a fibrous character, while distinctly nucle- 

 ated plastids, the so-called " decidua-cells," fill the mesh-spaces of 

 the reticulum. 



The villi of the placenta consist of a reticulum of plastids 

 with thickenings at the points of intersection, in close connection 



FIG. 48. MEDULLARY TISSUE OF BONE FROM THE SCAPULA OF A 

 NEW-BORN KITTEN. 



B, bone-tissue ; 8, myxomatous tissue composed of spindle-shaped plastids, traversed by 

 a capillary blood-vessel. Magnified 800 diameters. 



with the endothelial wall of the capillaries. Most of the mesh- 

 spaces exhibit central nuclei. (See Fig. 49.) 



The tissues of the body, which after more advanced develop- 

 ment show the structure of fibrous connective tissue, are origi- 

 nally reticular. In many instances we encounter in very young 

 embryos spaces, inclosed by a fibrous or plastid reticulum, which 

 contain a jelly-like basis-substance, too large for admitting them 

 to have originated from a single plastid. In some other instances 



