622 DR. ROLLESTON ON THE HOMOLOGIES OF CERTAIN 



superior coraco-brachialis, the origin of which is described in my account of the muscles 

 of the Sparrow-Hawk, be the homologue of the obturator interims, it is difficult to deny 

 the homology of the subscapulars (with the tendon of which its tendon fuses) with the 

 gluteus medius, which holds so much the same relation by its tendon to the obturator 

 internus. 



Leaving now the subject of the homology of the subscapularis and teres major with 

 the glutei, I may refer to the nerve-supply of the teres minor from the same nerve, the 

 circumflex, which supplies the deltoid, as showing that this muscle is really but a divari- 

 cation of the deltoid posteriorly, as a similar line of argument shows the tensor fasciae 

 femoris to be of the gluteus medius. The difficulty, therefore, as to the nomenclature of 

 the muscle, which in Saurians and the monotrematous Echidna (see Mivart, Trans. Linn. 

 Soc. vol. xxv. p. 384, and Proc. Zool. Soc. June 1867, p. 778 ; Stannius, Handbuch der 

 Zootomie, ii. p. 126) has been sometimes called "teres minor" and sometimes "a second 

 part of the deltoid," may be met by saying that the posterior factor of the "deltoid" 

 is not, in these lower animals, differentiated into a superficially placed " deltoid " and a 

 deeper lying " teres minor." There is ordinarily no infraspinatus differentiated from a 

 supraspinatus in either bird, saurian, or Crocodile. But both these latter classes possess 

 the muscle which, with the origin of the teres minor, has the insertion of the teres major, 

 and is called "subscapulo-humeral" by Macalister (Proceedings Royal Irish Academy, 

 December 1867) and Wood (Proceedings Royal Society, May 23, 1867, p. 534), " infraspi- 

 natus secundus" by Professor llaughton, "teres major" by Stannius (Zootomie, ii. p. 128, 

 2nded.), and, finally, "teres minor" by many anatomists, though incorrectly, if the 

 insertion is to determine the name and nature of a muscle rather than its origin. Meckel 

 (Vergleichend. Anatomie, iii. p. 512) uses this last nomenclature, speaking of a muscle 

 with the origin and insertion specified as a " teres minor," and stating that it is found in 

 the Horse, in Ruminants, in the Ai, and in the Mole. A few birds possess this accessory 

 teres major. In the common Powl it arises from the outer surface of the scapula, a little 

 way anteriorly to the downward-growing process, so well marked in the Galling and in 

 the Dodo, which receives the tendon of the anterior portion of the serratus anticus. It 

 is inserted on the posterior lip of the pneumatic foramen, a point serially homologous 

 with that of the insertion of the smaller glutei of human anatomy. 



This muscle is not possessed by the Common Pigeon, but it is found in the Common 

 Buzzard and Sparrow-Hawk, and in the Goose. The teres major pr< -per is of very large 

 size in ordinary birds ; it is present in the Crocodile, but absent in saurians. It is not 

 inserted with the latissimus dorsi in the Sparrow-Hawk, but passes to the anterior lip of 

 the entrance to the pneumatic foramen, to a point just opposite to that of the insertion 

 of the accessory teres major. 



In birds there is no prascapular region (Parker, Shoulder-Girdle, p. 113), and conse- 

 quently no supraspinatus. Indeed, as the supraspinal,,* of Meckel, I. c. p. 313 (no.xv. 

 Schoepss) receives its nerve-supply from the circumflex, and must he looked upon ... . 

 part of the deltoid, birds would appear to have no "suprascapular" muscles at all 

 unless we may consider the deeper fibres of the praglenoid head of the levator 



I 



Emu and Apteryx to represent such a muscle ; for there is such 



h 



a muscle 



