CHAPTER I. 

 DISEASES OF BONES. 



The diseases affecting bony tissues may broadly be divided into local 

 and general. Local diseases like ostitis, periostitis, necrosis, fracture, 

 etc., are somewhat rare, and are less important in cattle than such 

 general diseases as rachitis and osseous cachexia. 



Eachitis is a disease of young animals, and occurs during the growing 

 period. Osseous cachexia is a disease of adults. Nevertheless, there is 

 a relationship between these two morbid conditions, for they frequently 

 co-exist in one family. Moreover, brood mares and cows suffering from 

 osseous cachexia give birth to foals and calves, which, if left with their 

 mothers, almost inevitably become rachitic. 



The general characteristic common to both rachitis and osseous 

 cachexia consisting in diminution in the normal proportion of mineral 

 salts entering into the constitution of the bone, numerous theories have 

 been advanced to explain this irregularity in nutrition. 



The theory of insufflciency is one of the oldest. It presupposes that 

 the young animals' food contains insufficient mineral salts necessary for 

 building up the skeleton, hence rachitis ; or again, that the daily food 

 of the adults does not afford sufficient mineral salts to compensate for 

 the normal transformation which is continually going on within the 

 organism, and for the direct losses which occur through the medium of 

 the urine, milk, etc. 



This extremely simple theory appears perfectly logical, but unfortu- 

 nately does not fit in with all the observed facts. In reality, rachitis 

 attacks children whose supply of milk, from a chemical point of view, 

 leaves nothing to be desired. The same is true of animals, particularly 

 of young i^igs. The so-called "acid theory" has therefore been ad- 

 vanced to explain the points left obscure by its predecessor. 



The acid theory. According to this theory, the food may contain 

 more than sufficient mineral material without, however, preventing the 

 development of rachitis or of osseous cachexia. 



In animals suffering from digestive disturbance the alimentary tract 

 may become the seat of excessive fermentation or of changes in secretion. 

 There is thus produced an excess of lactic acid which passes into the 



B 2 



