OF THE ARTICULATIONS. 403 



pears. If it is in the haunch, the cotyloid cavity diminishes, 

 and from being hemispherical becomes triangular; a fact to be 

 added to those which show that the form of organs depends, 

 partly at least, upon their reciprocal action. It would appear 

 that these changes were in part known so early as the time of 

 Hippocrates. 



635. M. Chaussier* has produced, in dogs, the formation 

 of accidental articulations intermediate between the two kinds 

 above described. Having by an incision made the head of the 

 femur to come out of the cotyloid cavity, and having sawn it 

 below the trochanter, he brought the flesh together, and left 

 the animals to the care of nature. On examining the parts at 

 periods more or less remote, he found that the muscles had 

 drawn the extremity of the femur near a part of the ischium; 

 that the truncated bony extremity was rounded, and invested 

 with a cartilaginiform substance; that the point of the ischium 

 against which it rested had also assumed a cartilaginous ap- 

 pearance, and sometimes presented an articular fossette of 

 greater or less depth; lastly, that the cellular tissue formed 

 around this new articulation a kind of membranous capsule, 

 in which was contained a serous fluid in greater or less quan- 

 tity. 



636. The diarthrodial articulations may be altered in their 

 solidity and in their mobility; they may be too loose or too 

 tight, and they may also be luxated or anchylosed. 



637. Luxation is the more or less complete cessation of 

 the natural connexion between the contiguous surfaces of 

 bones. When it takes place, the ligaments are violently 

 stretched, drawn out, or even ruptured. The other articular 

 and surrounding parts are more or less affected by these lesions. 

 Motion is then very difficult. The most mobile articulations 

 are the most susceptible of it. Thus the arthrodiae and enar- 

 throses are those which present the greatest number of exam- 

 ples of it, and the close diarthroses those which present the 

 fewest. Of the articulations of the same species, those which 

 are the least close, those whose articular surfaces have the 



* Bulletin des Sciences par la Soc. Philom. Paris, an. viii, 



