NOTES ON PALEOPATHOLOGY. 681 



For the first week or more this exudation of reparative material 

 takes place at the point of fracture — occurring externally be- 

 tween the periosteum and the bone, and internally between the 

 medullary membrane and the bone. At the end of about three 

 weeks this provisional callus acquires a firmness about equal to 

 that of cartilage ; which, at the end of three months, both inter- 

 nally and externally, ossifies — the ossification being more or less 

 of a spongy nature. Shrinkage now takes place, and this spongy 

 ossification becomes modeled down, forming compact bone. 

 Still, at this stage the fractured ends are only united by fibrous 

 tissue, though the surrounding ossified callus holds them firmly 

 together. 



Finally, this provisional callus undergoes more or less com- 

 plete absorption, and the permanent callus forms directly between 

 the fractured ends of the bone. This results in the nearly com- 

 plete disappearance of the periosteal enlargement, and, internally, 

 in the re-establishment of the medullary canal. Normally, this is 

 the course of the union of fractures in long bones, of the charac- 

 ter referred to above, but there are a number of exceptions to it, 

 and irregular unions occur which do not require comment from 

 me in the present connection. 



Several years ago I obtained a turkey vulture (Cathartes aura) 

 that had survived a glance shot from a carbine ball which frac- 

 tured both bones of the left forearm of the upper extremity. It 

 had also sustained other fractures, all of which I fully described 

 in the New York Medical Journal (see No. 3 of foot-notes given 

 antea). This bird I subsequently killed with chloroform and pre- 

 pared its skeleton. Upon examination it was discovered that the 

 left ulna and radius were each fractured at the points shown in 

 the accompanying cut (Fig. 1),* and were at the time of its death 

 at that stage of union where the provisional callus is well under 

 way toward absorption. 



From my various observations in such cases I have arrived at 

 the conclusion that at this stage the weakest point in the provi- 

 sional callus lies in the plane of the meeting of that material, as it 

 is furnished by the two broken ends of the bone — in other words, 

 it is at its thickest part and in the plane of the fracture. I mention 

 this fact, as reference will soon be made to it again, further on. 



Owing to the support afforded by the quill-butts of the sec- 

 ondary feathers of the wing in a bird, acting as a compound splint 

 of Nature's furnishing, the radius and ulna in that class of verte- 



* I am under obligations to the New York Medical Journal for the loan of the electro 

 of this figure, and hereby tender my grateful acknowledgments for the same. The origi- 

 nal was drawn by me direct from my specimen, a number of years ago, and I still possess 

 the latter in my private cabinet. 

 vol. xlii. — 46 



