110 C. V. MORRILL 
scalpel. Then the part to be removed was grasped with the 
forceps and slight traction employed to draw the joint surfaces 
apart. The capsular ligaments were then divided with the 
scalpel and the limb removed, care being taken not to touch the 
skeletal parts remaining (hip bones or femur according to the site 
of operation). <A flap of skin and muscle was drawn over the 
wound and a couple of stitches taken. There was very little 
trouble from bleeding, but in cases where it was profuse, the 
specimen was discarded. 
1. Amputation at the hip-joini. Nineteen animals were used 
for this operation divided into groups of eleven, six and two. 
All of the first group were killed and examined between thirty- 
nine and forty-six days after operation. Externally each showed 
a small bud at the site of amputation. Microscopically the bud 
was composed of a dense mass of indifferent cells with small 
round nuclei. No change in the hip-girdle was observed. The 
second group of six were kept for six months. At this time all 
had regenerated a new limb about three-fourths the normal size. 
Microscopie examination showed the normal number of skeletal 
elements in the limb, each represented by a bar of cartilage. 
There was a well developed narrow cavity in the femur and 
peripheral ossification had begun in all the cartilages except 
the tarsals which do not ossify in these animals.? Joint cavities 
were well marked at this time. The third group of two animals 
was lost. Owing to the small number of specimens and the 
lack of intermediate stages, the successive steps in this type 
regeneration could not be made out. The detailed account of 
this process will therefore be based upon the larger and more 
complete series of operations at the knee-joint (vid. infra). 
2. Amputation at the knee-joint. About seventy-five opera- 
tions of this kind were made. Most of the specimens obtained 
were fixed at intervals, of from ten to fifty days and sectioned. 
The remainder were allowed to complete their regeneration to 
3 While it is true that peripheral ossification does not occur in the tarsalia, 
nevertheless an extensive marrow cavity is normally present and the irregular 
trabeculae of cartilage bordering it generally become calcified, if not actually 
bony. 
