DEVELOPMENT OF CONNECTIVE TISSUE. 87 



appearances above described pass immediately into the fol- 

 lowing. 



The nuclei, which in the first instance are ill defined, become 

 vesicular, with distinct double contours at their margins; 

 they are transparent, but contain in their interior a mass 

 of coarse granules elongated in the direction of the longer 

 axis. The cells become attenuated, and assume an elongated 

 spindle shape (fig. 4). The processes are here and there 

 knotted, branch sparingly, and are frequently connected with 

 one another by their extremities. Two enlargements con- 

 taining nuclei are often only connected together by a short 

 bridge of protoplasm, and with their processes present the 

 appearance of a bi-nucleated double fusiform mass. Fusiform 

 cells divided transversely may also in some instances, though 

 rarely, be seen. These long and beautiful fusiform cells appear 

 to be widely separated from one another by a clear substance, 

 in which, at an early period, nothing more may be perceived 

 than short interrupted sinuous lines. It is very remarkable 

 that between the above-described elongated cells other round 

 cells are scattered ; these exhibit a granular appearance, and 

 one or more round nuclei resembling those of the amoeboid 

 cells. The formation of these structures may be well followed 

 in the above-mentioned embryoes of sheep of from an inch and a 

 half to two inches in length, and here most beautiful examples 

 of the fusiform cells of embryonic connective tissue described by 

 Schwann and Virchow may also be seen. Such fusiform cells 

 occur also abundantly in the peritoneum of older embryoes, 

 but during their intra-uterine life they pass their prime. Their 

 processes in particular become attenuated, though they still 

 remain very long, and it requires considerable trouble to follow 

 them out to their termination. It is at this period that the 

 looped smooth unbranched fibrils first appear in small numbers 

 and scattered in the clear matrix between the cells. These, 

 crossing the cell processes at various angles, may be followed 

 over an entire series of fusiform cells ; in many instances, how- 

 ever, they attach themselves for a short distance to the long 

 axis of the fusiform cells, and appearances are then produced 

 which may easily lead to the idea of a connection between the 

 fibrils and the cells. But there are many other appearances by 



