54 Prof. A. Macalister on the Myology 



Pectoralis major, a large and flat muscle, arises from the 

 front of the sternmii, continuous with its fellow of the opposite 

 side, from the cartilages of the six upper ribs, and from the 

 inner end of the rudimental clavicle ; from this origin it is 

 inserted into the pectoral edge or outer lip of the bicipital 

 groove. It does not extend to the abdomen, as is the case in 

 Dasyjjus (Galton) ; and it likewise differs from the pectoral in 

 that animal by extending to the clavicle, which is not the case 

 in the Armadillo or in the Orycterope. The pectoral in the A'i 

 is not connected with the latissimus dorsi or with the external 

 oblique, but is closely attached to the deltoid. 



Pectoralis minor was absent in Bradyjjiis^ as stated by 

 Meckel. Cuvier, in his plate of this animal, calls the next 

 muscle by this name, erroneously, I believe. It is likewise 

 absent in the Anteaters and in the Armadilloes. Galton con- 

 siders the muscle described by Meckel in the Armadillo as 

 pectoralis minor to be in reality subclavius. In Orycferojnis a 

 pectoralis minor does in reality exist, described by Humphry 

 and Galton. 



Subclavius, a large muscle, arising as usual from the first 

 rib, passes upwards and outwards to be inserted into the under 

 side of the acromion process, and by a fcAV fibres into the cla- 

 vicle. In the Orycterope this muscle is large and sternal in its 

 origin ; and its insertion, in the specimens examined by Mr 

 Galton, Avas into a sesamoid bone beneath the acromio-clavi- 

 cular joint, imbedded in the fibres of origin of the deltoid. It 

 is present and large in the Armadillo, but absent in the Ta- 

 mandua (Rapp, Galton), and in the Great Anteater (Pouchet) 

 and Two-toed Anteater (Meckel) ; but it is present and small 

 in the Two-toed Sloth (Galton). 



Pectoralis quartus (latissimus dorsi secundus) arises from 

 the seventh and eighth ribs at the junction of their bony and 

 cartilaginous portions ; it is inserted into the outer or pectoral 

 lip of the bicipital groove. This muscle I consider to be a 

 fourth pectoral ; and its insertion is, I think, sufficient to deter- 

 mine this relation ; it is, however, often regarded as a part of 

 the latissimus dorsi, and has been described as a second latis- 

 simus in the Seal and several other animals. Galton, in speak- 

 ing about the latissimus dorsi in Dasypus sexcinctus^ says that 

 " certain muscular fibres take origin from the ribs between the 

 fifth and ninth inclusive, anterior, but close, to those costal 

 elements of the latissimus dorsi already described as arising 

 from the sarrie ribs, and pass straight u])wards to that ])ortion 

 of the l)road terminal tendon of the pectoralis major which has 

 the highest insertion into the humerus;" this he considers 

 possibly a modified " Achselbogen ;" and he states very pro- 



