THE FUNCTION OF REISSNER’S FIBER a 
characteristic knot, a careful examination of this mass will, 
almost invariably, reveal the fact that the retraction was ac- 
complished by a spiral winding of the fiber. 
Such a knot of retracted fiber has, indeed, the form of a con- 
torted mass similar to that which may be produced in any thin 
stretched elastic thread of which one end is held fast and the 
other end twisted continuously in one direction. I have been 
able to obtain practically all stages intermediate between such 
complicated knots and the simplest spiral (text-fig. 2). Unlike 
D. 
a eee ac 
| E. f 
G. Meee 
UT ORIRS — SASHECKERR, 
Text-fig. 2 Stages in the twisting of Reissner’s fiber in its withdrawal from 
the point of breakage. A, B, D from Scyllium eanicula (9); C, from Petro- 
myzon fluviatilis; HZ, F, G, H, from Raia blanda (3). 
the simple twisted elastic thread, however, the spiral winding 
may appear interruptedly in Reissner’s fiber, spiral stretches 
alternating with swollen but untwisted lengths. Moreover, the 
twisting does not always make its appearance at the free end 
but may arise at a greater or less distance from the point where 
the fiber has been broken. 
If, therefore, the spinal cord has been cut prior to fixation, 
Reissner’s fiber may be found to have withdrawn for a relatively 
considerable distance from the point of section and a great stretch 
of the central canal may be found devoid of fiber. The extent 
of such retraction apparently varies with the region in which the 
