MUCOUS TISSUE 63 



the intercellular substance, apart from the cells, and Merkel defends this 

 idea in the following passage, here somewhat abbreviated (Anat. Hefte, 

 Abt. i, 1909, vol. 38, pp. 323-392): 



The mesenchymal syncytium secretes an amorphous gelatinous substance, which 

 may be scanty (as in reticular tissue) or abundant (as in the umbilical cord) . The fibers 

 arise exclusively in this gelatinous substance; the cells take no direct part in the forma- 

 tion of the fibers but serve only for the production of the jelly. At their first appearance 

 the fibers are not collagen, and generally they are not yet smooth and glistening like 

 true connective tissue fibers. Instead they are granular, and not infrequently varicose. 

 Later, though often very soon, they acquire the characteristic appearance of fully 



a- 



FIG. 51. Mucous TISSUE OF THE HUMAN UMBILICAL CORD, STAINED WITH PHOSPHO-TUNGSTIC ACID 



H*MATOXYLIN. (Mallory.) 

 a, White fiber, b, fibroglia. 



formed connective tissue fibers. They may arise as a very delicate network, which, 

 through the breaking down of the least utilized threads, becomes transformed into 

 smooth and unbranched fibers. But in places where from the first there is a decided 

 stretching, as in tendon, parallel unbranched fibers are formed directly. Professor 

 Heiderich has shown me preparations of a mucin, in which, by the addition of acid, 

 structures were formed which were strikingly similar to developing connective tissue 

 without any stretching, nets with round meshes; but with the slightest traction, long 

 fibers isolated from one another. Thus connective tissue fibers are merely the effects 

 of mechanical conditions upon the gelatinous intercellular substance. 



A very different idea of the origin of the white fibers is that of Flem- 

 ming, recently further elaborated by Meves (Arch. f. mikr. Anat., 1910, 

 vol. 75, pp. 149-208), according to whom the fibers arise within the cyto- 

 plasm. By special methods Meves has demonstrated coarse filaments, 

 which he names chondrioconta, within the protoplasm of both epithelium 

 and mesenchyma. These granule-rods or chondrioconta (probably 

 comparable with the mitochondria of gland cells) are regarded as a part 

 of the fundamental protoplasmic network or spongioplasm. If they 

 are short they are called chondriosomes. Meves describes the develop- 

 ment of white fibers as follows: 



