TISSUES, ORGANS, AND SYSTEMS. 95 



great mass of the organs composed of connective tissue, it is incorrect. 

 The possibility of making out fibrils in delicate membranes, even with- 

 out preparation, the ease in which these may be isolated in tendons and 

 ligaments, and lastly, the circumstance that the fibrils may be demon- 

 strated upon transverse sections of the tendons, and of the more solid 

 connective tissue in general, are for me sufficient reasons for retaining 

 the old view. 



With respect to the development of the connective tissue, I distinguish 

 two types which correspond with its two principal forms, the solid and 

 the areolated. The former is developed out of masses of cells without 

 any demonstrable matrix, by the elongation of the cells, their breaking 

 up into fibrils, and their coalescence. This is most obvious in the ten- 

 dons and ligaments, which, as observations upon Batrachian larvye and 

 upon mammalian embryos show, at first consist entirely of common, 

 rounded, formative cells, which about the same time as the transversely 

 striated muscles are formed (in mammalia in the second month), become 

 fusiform. The further development demonstrates (what had escaped 

 Schwann) that only one portion of these fusiform cells, and in fact cells 

 which are remarkable for their size and paler contours, become bundles 

 of connective tissue, while the others, which Schwann in part depicts 

 rightly (Tab. III. fig. 11 ; the smallest cell, fig. 6, from connective 

 tissue, the cell 6, and the lowest cell upon the right side), remain for a 

 time as fusiform elements, and only subsequently become fused into 

 elastic fibres. There arises, at last, out of the cells alone, with no dis- 

 tinguishable matrix, a compact tissue composed of two chemically quite 

 distinct fibres. The areolated connective tissue differs from the former 

 in the circumstance that, if not from the beginning yet from the time 

 at which the cells become elongated, an abundant gelatinous interme- 

 diate substance is developed between them, which does not yield gela- 

 tine, ami never becomes converted into it, but contains albumen and a 

 substance similar to mucus ; Schwann, indeed, found a substance re- 

 sembling pyin, in this tissue. Although all embryologists know that 

 the areolated connective tissue is at first of a gelatinous consistence, 

 as for example, under the skin, in the neck, in the omentum, behind the 

 peritoneum, in the orbit, and in the bones, no one has yet drawn atten- 

 tion to the general occurrence of that intermediate substance which 

 was observed by Schwann in a single locality. I originally became ac- 

 quainted with this tissue between the chorion and amnion, and at first 

 paid more attention to its reticulated anastomosing cells. Subsequently 

 when I examined it more closely in the enamel organ of the embryonic 

 tooth sac, I paid attention to the peculiar intermediate substance, and 

 at the same time Virchow described this tissue from the umbilical cord, 

 where the gelatinous tissue of Wharton entirely consists of it. Virchow 

 believed that it ought to be distinguished from connective tissue, and 



