The Bulletin 
11 
The course of the septa, whether in persisting ensheathing callus or 
in the bone itself, takes a changed direction in accordance with the al¬ 
tered transmission of weight through the hone and the different angle 
at which the muscles pull. 
Where the ends of the fragments overlap, the. ensheathing callus 
fills up the angles; and while the open end of the medullary canal in 
each fragment in thus closed, its continuity through the hone is re¬ 
stored by the absorption of the intervening walls of the contiguous and 
overlapping fragments. Where the fragments are not in contact, the 
intervening space becomes filled with the ensheathing callus, which is 
then sometimes called interposed callus. Where the fracture is com¬ 
minuted, the splintered fragments become glued, as it were, together, 
and to the main fragments by the ensheathing callus formed from the 
vascular tissue in which they become surrounded. When the fragments 
are in good apposition and are kept relatively at rest little ensheathing 
callus is found; but where there is much displacement, or where rest is 
impossible, as in a fracture of a rib, or difficult to obtain, as in a frac¬ 
tured clavicle, a considerable amount is produced. 
The series of studies here presented are of two kinds: First, a study 
of the reparative processes; second, a study of the means of control of 
the fracture and care of the bird. 
Figure 1 illustrates the study of a series of fractures that have been 
repaired for a considerable length of time. A shows a repaired ulna 
which has sustained an angular break, with a sliver of bone split off 
of the upper side and extending nearly to the proximal end of the bone. 
1 shows the repair and a porous provisional callus. At 2 is shown that 
the reparative bone material has been lavishly used. Letter C, ISTos. 
6 and 7, show the same. Letter B shows a tibia and fibula of a hen which 
has sustained a fracture at right angles to the shaft of the bone —(3 is 
the fibula; 1+ the tibia; 5 the repaired fracture). That this fracture has 
been repaired a long time is indicated by the fact that practically all of 
the provisional callus has been removed by absorption. Letter D shows 
the bone at a different angle, and shows at 8 the fibula, at 9 the tibia, and 
10 the repaired fracture. This bone was improperly cared for, and 
hence a crooked leg was the result. 
A series of studies were made of the nature and rapidity of repair 
of fractured bones of a domestic fowl. The birds were chloroformed 
and the bones fractured and set while the birds were under the anesthesia. 
The metatarsus and ulna were selected. The material used to hold 
the bones in place were cotton, one-inch cotton cloth bandage, wooden 
splints, and glue. At the end of each experiment the bird was again 
chloroformed and the bone removed. After a physical examination of 
the bone it was sectioned longitudinally, photographed, and the lesion 
