620 DR. ROLLESTON ON THE HOMOLOGIES OF CERTAIN 



tions. A very similar position, I may observe, is instinctively assumed by a man when he 

 uses his pectoral muscles for the purpose for which quadrupeds ordinarily employ them, 

 viz. for raising and supporting the trunk upon the fore limbs. And an observation of the 

 position assumed by a man who puts himself into a quadrupedal posture for the purpose 

 of drinking at a stream, or who raises himself by the help of his arms from a low seat 

 by placing his hands on the table at which he is sitting, will illustrate the relations of 

 the extensor and flexor, and of the inner and outer aspects of the two limbs, as well as 

 the most detailed parallelization of the skeletal elements. 



Secondly, a study of Mr. Parker's descriptions and histories of the shoulder-girdle will 

 leave no doubt on the mind of any one, I apprehend, as to the serial homology of the 

 coracoid with the ischium, and of the prcecoracoid with the os pubis. The shoulder-girdles 

 of the .Frog and the Chelonians are especially instructive when compared with the pelvic 

 girdle of the Crocodiles. Express utterances as to the relationship of the two sets of 



bones may be found in Mr. Parker's work < On the Shoulder-Girdle and Sternum,' at 

 pp. 7, 59, and 83. 



Professor Huxley's view (which has been adopted by Mr. Mivart, and a similar one to 

 which, I am informed by Professor Turner, of Edinburgh, was entertained by his prede- 

 cessor Professor Goodsir), as to the homotypical relationship of the sabscpidaris and teres 

 major, not to the iliacus and psoas, but to the middle and smallest glnte»s, is a third point 

 for discussion, and one which does not admit of being decided quite so cursorily as the two 

 I have already glanced at. Eor the acceptance of this apparent paradox, it is necessary 

 first to accept the principle that the true homology of a muscle is to be determined by 

 its insertion (see Mivart, Trans. Linn. Soc. vol. xxv. p. 398 and 400). To this principle I 

 should give a general assent, without forgetting that we may find exceptions to it, such 

 as the insertion of the pectoralis major of the Sparrow-] I awk into both t ul, rosities of the 

 humerus, such as the occasional insertion, in the way of corollary to thif first exception, 

 oi the pectoralis minor into the outer tuberosity of that bone, or such, thirdlv, as the 

 insertion of the psoas of the Crocodile on the outer, while the iliacus is inserted on the 

 inner side of the femur. In these cases, however, rudiments at least of the primitive 



^V , ^ ° f a P° neui ' otic b ^ds will ordinarily be left remaining, as if to 



been, so to say, not by an arbitrary transference, but by a gradual 



indicate that it 



ateral extern that the alteration of the point of attachment has been effected 



lie essential character of a muscle may he considered to be as lit . le affected by these 



ransgress.ons of its ordinary limits laterally, as the essential character of a muscle which 



w ordinarily inserted mto the proximal segment of a limb is considered to be affected 



nnatrT r P1 t "p ti0n int ° * dlStal SeSment ' ^ foscia or aponeurosis, ,vl,i,-h may 



S 2 1 llu 1 T^ teUd ° n ' Therc Me ' h0WWer ' th ™ «*» °f anatomical facts to 

 el on f ie v" , 01 Y S ^^ S6em t0 me t0 make the ''--I of the homotypical 



2? less of IT n T?T WlUrk ' aml the ranki "S of th, latter muscle with the 



e ntiarcha \ " ^f ** ^ ^ be ™ reasonable *«" ** th " 

 Zmt^ bv , T SCle * haVe Called " ^raco-humeral - in the Crocodile, is 



oufc" urfl? o f t r^ e D r d % the iDSerti0n M ™ d ^S - of »• tendon on the 



outer surface of the humerus between those of the pectorcdU m „jor and deltoid. Yet, 



