DEVELOPMENT OF CONNECTIVK-TISSTE FIBERS. 57 



preparations in which the mitochondria have been destroyed. It is very similar 

 to the structure which forms the fibril of the muscle-cell (plate 2, fig. 6). 



Mislavsky (1913) was able to differentiate a plasma fibril as well as mito- 

 chondria in the kidney tubule cells. He found that while the plasma fibrils 

 stretched entirely across the cells MS straight lines, the mitochondria did not pass 

 to the walls of the cells. 



In the cultures studied mitochondria did not fuse into strands or become 

 arranged in rows to form the connective-tissue fibrils. In all of these observa- 

 tions, while the mitochondria at times remained caught within a bundle of fibrils, 

 the fibrils themselves originated from the exoplasm of the cell. 



OTHER GRANULES AND "GRAINS DE SEGREGATION" OF THE 

 CONNECTIVE-TISSUE CELL. 



The connective-tissue cell ordinarily contains very few fat globules, and fre- 

 quently none at all. When present they are small, round, highly refractive globules, 

 which usually lie near the nucleus and which stain in the manner characteristic 

 for fat. 



In addition to the mitochondria granules in the cells, there are a number of 

 small, round granules, which can be distinguished from the granular type of 

 mitochondria only by the 'rapidity of their movements and by certain vital dyes. 

 These granules stain blue with pyrol-blue, purple with brilliant cresyl-blue, and 

 red with neutral red. In the fixed preparation they frequently take certain of the 

 mitochondrial stains, and especially do they take the same purple color as the 

 mitochondria with Benda's stain. 



The vacuoles of Lewis and Lewis (1915) correspond more or less with the 

 grains de segregation of Renaut (1904, 1907) and Renaut and Dubrieul (1906), 

 which these observers found to stain with neutral red and which they claimed 

 formed fibrils through a secretory activity of the cell. These bodies are present 

 in the connective-tissue cell, sometimes in large numbers (plate 2, figs. 2 and 3), 

 but so far as could be determined they take no part in the formation of the fibrils. 



TENDON. 



Only a few growths of cells which could be definitely identified as tendon- 

 cells took place, and in these growths the formation of the fibrils occurred in a 

 manner somewhat different from that of the formation of the fibrils of the sub- 

 cutaneous tissue. The tendon-cells were arranged as narrow, elongated cells, more 

 or less parallel, and the fibrils developed as clear lines along the surface of the 

 cells. These delicate lines joined into bundles from one cell to another in mark- 

 edly parallel lines (plate 2, fig. 8). In preparations stained with Mallory's con- 

 nective-tissue stain the fibrils stained blue. 



