ETIOLOGY AND OCCURRENCE 19 



the periosteum is left intact or nearly so, no crepitation is dis- 

 cernible. If this fracture is simple, prompt recovery may be ex- 

 pected. Bones of young animals, because they do not contain 

 proportionately as much mineral substance as do bones of adults, 

 are more resilient and less apt to become completely fractured. 

 They are, however, subject to what is known as green stick 

 fracture. 



Impacted fractures are usually occasioned by falls. When the 

 weight of the body is suddenly caught by a member in such man- 

 ner as to forcefully drive the epiphyseal portions of bone into 

 and against the diaphysis, niultiple longitudinal fractures occur 

 at the point of least resistance. Parts so affected undergo a 

 fibrillary separation, increasing the transverse diameter of the 

 bone; or if the impact has been sufficiently violent, the portion 

 becomes an amorphous mass. 



In a treatise on the subject of lameness, the bones chiefly con- 

 cerned and most often affected must be especially considered. 

 The shape and size of a bone when injured, determines in a 

 measure, the course and probable outcome in most cases, but of 

 first and greater importance is the function of the bone. A frac- 

 ture of the fibula in the horse need not incapacitate the subject, 

 but a tibial fracture is serious and generally proves cause for 

 fatal termination. The body of the scapula may be completely 

 fractured and recovery will probably result in most cases without 

 much attention being given to the sul)ject, yet a fracture of the 

 neck of this same bone constitutes an injury of serious conse- 

 quence. The difference in the function of different parts of this 

 same bone, as well as its shape and mode of attachment, deter- 

 mine the gravity of the case ; so it is in fractures of other bones 

 with respect to the course and prognosis of the case — function 

 is the important factor to be considered. 



Next in importance is the age of the animal suffering fracture 

 of the bone. Capacity for regeneration is naturally greater in 

 a vigorous, young animal than in aged or even middle-aged sub- 

 jects. A healthy condition of the bone and the body favor the 

 process of repair in case of fracture, and prognosis may be favor- 

 able or unfavorable, depending upon these factors mentioned for 

 consideration. Individuals of the same species, differing in tem- 



