236 GUTH
stimulation of the cord below the lesion elicited electrical activity in
the cord above the lesion. Windle continued these experiments on cats
and monkeys at the NIH, and although locomotor function was never
restored, his work proved that injured spinal cord nerve fibers retain
their growth potential in adult animals. His research, publications, and
symposia kept alive the interest in CNS regeneration for several decades
and led to the present large-scale research efforts aimed at achieving
functional regeneration of the injured spinal cord.Windle–Perfusion Fixation
One of the first weekly laboratory meetings in 1954 was devoted to the
problem of obtaining histological preparations that were free of artifact
ual changes (e.g., shrinkage, swelling, etc.). At the time, I did not
understand the full significance of what was being discussed, but I do
recall how impressed I was by the section chiefs’ unanimous agreement
that fixation by vascular perfusion was an essential step in preparing
tissues for light microscopical histology. Only later did I learn that
Windle and his colleagues had published in 1945 a seminal paper on the
importance of perfusion fixation.^7 At that time, the concept of perfusion
fixation was novel (for example, it was not even mentioned in Davenport’s
1945 book on histological technique^8 ). Nevertheless, its importance
remained largely ignored for another two decades, and was still not
considered worthy of mention in Ralph Lillie’s widely-used 1965 refer
ence book on histopathological technique.^9
The reluctance of anatomists to accept perfusion fixation was not
based on tradition so much as on scientific skepticism. For 50 years,
both basic scientists and clinical pathologists had been fixing their
tissues by simply dropping the specimens into a fixative solution, and
most of them, being satisfied with the quality of preservation, felt no
need for a change. Of course the continued testing of alternatives and addi
tives to 10 percent formaldehyde during this time (e.g., Heidenhain’s “susa”
which added mercuric chloride, Bouin’s fluid which added picric acid,
and Zenker’s solution which added chromic acid) should have provided
a warning that achieving adequate tissue preservation was no simple
matter. Nevertheless, the full significance of this issue was not recognized
and accepted until Cammermeyer, Palay, and many others demonstrated