OUTGROWTH OF THE XERVE FIBER 
815 
extent and manner of ending was therefore not observed in all 
fibers — nfi, and n/2, for instance, being only incompletely re- 
corded. The cell to which the fibrin filaments were attached is 
now drawn completely out of the main cell mass. Twelve hours 
later the longest fiber is found to extend 557 /x beyond the point 
of ending the evening before, having thus grown at the rate of 
46m an hour, the total length now being about 1.15 mm. Many 
branches are present and many new fibers are visible in the same 
region, but the proximal part of those described has become 
covered over by the loose cells which have wandered out from 
the main mass. These circumstances rendered it impossible to 
make further accurate observations of the changes which took 
place, and the specimen was therefore preserved. Unfortunately, 
the region which had been observed most carefully was com- 
pletely disarranged in the course of fixation and the preparation 
in Dermanent form was almost useless for further purposes. 
This same preparation showed a number of other fibers of inter- 
est. Among these was one which arose from a single isolated 
cell, and which was visible throughout its entire length (fig. 21). 
When first observed this fiber had a total length of 453^- At a 
distance of 303^ from the cell it bifurcated, the longer branch 
being 150m, and the shorter, which afterward grew to be the 
longer, 107m. At this time, the ends were not very active and 
that of each branch was almost globular, with but one blunt pseudo- 
podium. The cell itself was unipolar. Examined at the expir- 
ation of four hours and three quarters (fig. 22), the change in the 
fiber was found to be very great. The cell itself was unchanged 
but the fiber then had a total length of 631m, and one of the orig- 
inal branches had again bifurcated. All three of the terminal 
enlargements were exceedingly active, and all were provided with 
a number of fine filaments. The increase in length from the cell 
to the tip of the longest branch was 221m, which is at the rate of 
.77 H-M per minute, or 46.5m, per hour. Comparison of the two 
stages shows that the greater part of this was due to terminal 
growth, but the distance between the cell body and the first bi- 
furcation increased 21m, and the curvature of this part of the fiber 
was partially straightened out. 
