12 Cc. V. MORRILL 
regeneration after amputation through a bone. This difference 
has to do principally with the behavior of the distal epiphyseal 
cartilage of the femur. This epiphysis (fig. 1, Hp.f.) becomes 
slowly detached from the shaft by resorption of the bone and 
calcified cartilage (C.c.) proximal to it.2 The resorption seems 
to be brought about largely by the action of cells which arrange 
themselves along the surface of the bone or calcified cartilage 
and erode it. Many of them are giant cells. Their origin was 
not determined. Both Wendelstadt (04) and Glaeser (10) 
have described this resorption process by giant cells. Figure I 
shows the distal end of the shaft (8.f.) broken up into irregular 
fragments of bone and calcified cartilage. 
Coincident with the resorption process, a change takes place 
in the epiphysis itself. The cartilage matrix begins to break 
down. This occurs first on its distal and proximal surfaces 
(fig. 1, Hp.f.). There is no evidence, however, that the cartilage 
cells themselves undergo degeneration. Indeed, in many in- 
stances they have been seen dividing mitotically and further, 
as the lacunae are opened by the degeneration of the matrix, the 
cells pass out and mingle with the surrounding tissues. Those 
liberated on the distal surface could not be further traced but 
on the proximal surface, that is facing the marrow cavity (figs. 
1 and 2, M.C.), they contribute to a mass of tissue (Az.C.) 
which is forming between the old epiphysis and the shaft. This 
mass which quickly takes on the appearance of young cartilage 
may be called axial cartilage adopting Glaeser’s (’10) term. 
This axial cartilage appears to have a two-fold origin: (a) 
from the liberated cells of the old epiphysis as stated above and 
(b) from the cells lining the marrow cavity and covering the 
trabeculae of bone and calcified cartilage at the distal end of the 
shaft; in other words from the endosteum. ‘These latter cells 
appear to increase in number and, streaming out from the interior 
of the femur (fig. 1) become massed under the old epiphysis 
where they form the main contribution to the new axial cartilage. 
5 It may be stated that there is normally a considerable amount of calcified 
cartilage at the plane of union of shaft and epiphysis. This is distinct from the 
uncalcified, hyaline cartilage of the epiphysis itself. 
