ACTING FACETS OF ARTICULAR SURFACES. 261 



elimination or removal of such portions of one or both of the 

 elements in their typical form (that is, in the forms which 

 they would possess in virtue of their completed geometrical 

 construction), as are not absolutely essential to their efficient 

 action. Thus, for example, as one essential condition of 

 efficiency of an articular couple is the provision of a sufficient 

 extent of perfect contact in the negative phase, an articular 

 couple would act efficiently, although the whole of the proxi- 

 mal margin of one of the elements were removed, along with 

 as much of the remaining portion of that element as would 

 retain in reserve enough of the proximal extremity of its dis- 

 tal or antipolar margin for contact, during the negative phase, 

 with the distal or antipolar portion of the polar margin of the 

 opposite element ; or, expressing the matter in less precise but 

 more direct terms, the couple would act efficiently as regards 

 its passage to its negative phase, although only the polar or 

 proximal extremity of one of its elements were reserved, and 

 the place of its removed portion supplied by soft, yielding, 

 or elastic textures. It is obvious, however, that if only the 

 polar portion of one of the elements be retained, a certain ex- 

 tent of the opposite element may be dispensed with namely 

 the distal and antipolar portion of its distal margin. Both 

 elements of a couple may, therefore, be more or less restricted; 

 but as, however much the polar margin of the one element 

 may be curtailed, the corresponding margin of the opposite 

 element must be reserved, I employ, as stated in paragraph 

 5, the term restricted to designate the element with the cur- 

 tailed, and the term reserved to designate the element with the 

 retained, polar margin. As the object of the present com- 

 munication is to record the general principles involved in the 

 inquiry, I reserve for succeeding communications on special 

 points all details relating to articular elements, couples, and 

 combinations, as well as their relative adjustments by means 

 of ligaments, nbro-cartilaginous menisci, and synovial pads. 



