POINTS FROM WHICH THE PROPORTIONS ARE STUDIED. 373 



4th. Metatarso-phalangal Axis. Point of ex- 

 ternal localization : at the superior insertion of the 

 corresponding lateral ligament of the articulation. 



All these points of localization the points where 

 the centre of rotation can.be located externally can 

 with a little practice be easily recognized in the liv- 

 ing animal. But it is indispensable that this habit 

 should be acquired by numerous experiments ; other- 

 wise, those who explore and measure are exposed to 

 almost inevitable mistakes. Nor are all subjects 

 suitable for such an experiment ; there are some 

 that must be absolutely rejected : those whose state 

 of obesity conceals not only from sight but also 

 from touch those external points of which we have 

 been speaking. 



These restrictions being established, we will 

 suppose that upon a chosen subject all the articular 

 centres have been marked with a colored pencil or 

 chalk. In order to obtain the imaginary axes of 

 movement of the osseous levers it will be sufficient 

 to join these points by straight lines. 



This direction should be determined accurately 

 in a special manner for the shoulder, the coxa, and 

 the phalanges, which are connected with only one 

 articular centre. All the other re- 

 gions are indeed placed between two 

 of these centres, and therefore as soon 

 as the latter are discovered their 

 direction is known. 



It is M. Lemoigne's opinion, as 

 well as ours, that the line of direc- 

 tion of the shoulder starts from the 

 scapulo-humeral centre, and supe- 

 riorly divides the dorsal border of the 

 scapula at about two centimetres be- 

 hind the line of the scapular spine. 



That of the ilium extends from 

 the coxo-femoral centre to the angle 

 of the haunch, which it divides in 

 its middle. 



Finally, that of the phalanges 

 extends from the metacarpo- or 

 metatarso-phalangal centre to the 

 ground, and remains almost parallel 

 to the anterior profile of the digital 

 region. 



The animal being placed and 

 maintained in its normal equi- 



FIG. 135. 

 1. Large toise 

 used as a compass 

 of thickness. 

 I 2. Compass of 

 thickness prop- 

 erly so called. 



