No. 514] ARTICULATIOXS OF CUISOlhS 



583 



nules; pinnules are borne upon the muscular fossae of 

 muscular articulations; in the projection of one straight 

 muscular articulation upon another to form the synarthry, 

 the interarticular ligaments and the muscles arc cut out, 

 and only the dorsal ligament remains; with the elimina- 

 tion of the muscular fossae, the pinnule sockets are lost; 

 hence, synarthries can never hear pinnules, as the pin- 

 nule-bearing element of the articular face is omitted from 

 their composition. Synarthries never affect the pinnula- 

 tion; if a pinnule be borne on the left side of a straight 

 muscular articulation preceding a synartliry, the pinnule 

 on the next succeeding straight muscular articulation will 

 invariably be upon the right side. A synartliry is pri- 

 marily composed of two coalesced succeeding muscular 

 articulations, one of which potentially bears a pinnule 

 upon the opposite side from that of the other; these two 

 primitive elements of the synartliry, being of exactly op- 

 posite tendencies in respect to their pinnules, counteract 

 each other upon being merged, and hence we find the syn- 

 artliry neutral in regard to pinnule arrangement; the 

 synarthry possessing primarily (morphologically) two 

 pinnules, the next following muscular articulation has its 

 pinnule thrown to the opposite side of the arm from that 

 on the muscular articulation preceding. Thus a syn- 

 arthry, in reality, instead of having no effect upon the 

 pinnule arrangement, has a double effect (though with 

 the same result), throwing the pinnule to one side of the 

 arm and back again within the compass of a single 

 articulation. 



Muscular articulations are frequently doubled, thus 

 forming an axillary from which two similar arms arise; 

 synarthries are never doubled ; they are already double 

 articulations, and a further doubling would be equivalent 

 to a quadrupling of muscular articulations. 



The syzygv is different from the synarthry only he- 

 cause it is formed from two oblique instead of straight 

 muscular articulations (Figs. 9 and 10). A rotation of 



