Preface. xi 



Skull have been kept separate from those of the rest 

 of the skeleton ; but with this exception, " locality " has not 

 been used as a basis of subdivision in this Series. Never- 

 theless, an examination of the groups formed will show 

 that " locality " has accompanied the " results " due to the 

 various " causes " in a remarkably close way. Thus there are 

 various forms of necrosis, caries, and enlargement, depending 

 upon different causes, and showing corresponding differences, 

 1)ut also locating themselves mainly in different bones, or forms 

 of bone tissue. " Locality " might therefore have been used as 

 subsidiary to " result " through all the groups of bone disease 

 had it seemed necessary. Among joints, on the other hand, 

 " locality " has been considered of more importance, and has 

 been used to divide and subdivide the specimens ranged under 

 the various causes of Inflammation. In every case we must 

 remember that "the division must be founded upon one 

 principle or basis," -i.e., " some quality or circumstance," which, 

 in order to be taken as the basis of sub-division, "must be 

 present with some and absent with others, or must vary with 

 the different species comprehended in the genus."* What that 

 basis is will depend upon the general character of the specimens, 

 the state of knowledoe at the time the classification is made, 



O 



and the judgment of the classifier. 



It is true that some forms of cross-classification still remain, 

 but while they seem inevitable, they are less likely to confuse 

 than those now excluded. Thus, for example, many diseases of 

 joints affect chiefly the bones ; compound fracture may lead to 



* Jevons' "Elementary Lessons in Lo^ic,"' 1893, p. 105. 



