36 



less cartilaginous toward their upper and posterior part." If 

 the structure of a tissue is any indication of its function, as I 

 believe it will be found to be, then the function of the inferior 

 cartilages is not precisely that of the lateral cartilages, for we 

 find the former much more fibrous in character than the latter; 

 and it is remarkable that the lateral cartilages themselves pos- 

 sess a fibrous border where the stellate ligaments are inserted, 

 and posteriorly where it is connected with the inferior cartil- 

 ages it assumes a more fibrous character generally. The infer- 

 ence is irresistable, drawn from the structure of these cartilages 

 alone, that the lateral cartilages fulfill the office of a pair of side 

 springs, having the property of yielding and rebounding with 

 every motion of the foot, and aiding and regulating in some 

 measure the vertical movements of the elastic tissues of the 

 frog, through the medium of the stellate ligaments superiorly, 

 while inferiorly it is kept in position, aided, and undue move- 

 ments controlled by the strong and comparatively unyielding 

 character of the inferior cartilages. 



The lateral cartilages are subject to ossification, that is to 

 say, of becoming converted partially or wholly into bone. En- 

 largements are not unfrequently met with, of one or both car- 

 tilages. These are not necessarily ossifications, but they are 

 evidences of a derangement of structure and function, the 

 causes of which will be discussed further on. 



The lateral and inferior cartilages are covered by a dense 

 tough membrane called the perichondrium, which performs a 

 similar office for cartilaginous to that of the periosteum for 

 osseous structures. 



ARTICULAR CARTILAGE. 



This is sometimes referred to as cartilage of encrustation, 

 because this particular kind is only to be found encrusting or 

 adhering to the articular surfaces of bones. As some theorists 

 on the pathology of navicularthritis deem this disease to have 

 its origin, as a rule, in the disorganization of this structure it 

 may not be uninstructive to learn somewhat of its nature and 

 uses. 



