APPENDIX. (43) 



*' In the dlllocation downwards the fuprafphiatvis will be on w.^'tniSwa. 

 the ftretch, the fubfcapnlaris and infrafpinatus will have their 

 fibres lengthened, and their direction altered, in confequence of 

 the head of the humerus being thrown below the glenoid cavity. 



" When the bone is diilocated outwards, and reds on the 

 dorfum fcapulas, the fituation of the mufcles will be nearly the- 

 following : The fubfcapularis and fuprafpinatus will be both 

 very much ftretched, while the infrafpinatus, having the hume- 

 rus thrown under it, will be relaxed, and a number of its fibres 

 will be torn from the fcapula, to make room for the head of the 

 bone. 



" In the third fituation, when the bone is luxated inwards, 

 the fuprafpinatus and infrafpinatus will be on the ftretch, while 

 the fubfcapularis Will be relaxed, and in the fame fituation as its 

 oppofite mufcle has been defcribed in the preceding fpecies of 

 diflocation. 



*' This account is drawn from the natural fituation of the 

 parts, and the few cafes of diflocation where there has been an 

 opportunity of diffedling the arm. It may be obferved, that in 

 all the three fpecies of luxation, the fuprafpinatus and deltoid 

 are put much upon the ftretch, the laft in a lefs degree. From 

 this we may infer the propriety of relaxing thefe mufcles com- 

 pletely during the time of redudion ; and this is another reafon 

 for raifing the arm when we attempt to replace the bone. 



"Mr Thomson * fpeaks of the head of the humerus being 

 caught between the tendons of the infrafpinatus and teres mi- 

 nor, as in a noofe ; this can happen only in the luxation out- 

 wards, and is one reafon for relaxing them completely in at- 

 tempting redud:ion, by throwing the arm towards the fide of 

 the fcapula, oppofite to that where the head of the bone is lying. 

 Having mentioned the fituation of the mufcles, I fliall now 



(F 2) point 



* London Medical Obfervations, vol. 2. p. 354. x 



