162 ANATOMICAL TECHNOLOGY. 



CLAVICULA (Fig. 30, 48, 66, 67, 72). 



The clavicle or collar bone is briefly described in 212. 



References. Straus-Durckheim, A, I, 509 ; Flower, A, 228; Gegenbaur (Lankester), 

 A, 477 ; Gegenbaur, C ; Gray, A, 215-218 ; Quain, A, I, 84, 96 ; Parker, A, 215 ; Hum- 

 phrey, A, 359-363. 



422,, Explanation of Fig. 48. This represents the unusually large and well 

 marked clavicles or collar bones of an old male cat. Their mesal or sternal ends are 

 apposed, and are seen to be approximately cylindrical. 



The left is placed in nearly its natural 



TnesaL x-v attitude in the body, showing that its cenhalo- 



caudal diameter is nearly ufiifofm, and that 

 eac ^ L en ^ curves slightly caudad, the mesal 

 FIG. 48.-THE RIGHT AND LETET CLA- end the more dccidedl y- 



VICTIM OF AN OLD CAT; x 1. The ri S ht is so P laced as * show tlie 



caudal aspect, and display the dor.sal concav- 

 ity. The mesal half is nearly straight, but the lateral is quite regularly curved. The 

 dorso-ventral diameter of the bone increases gradually toward the lateral end, which is 

 about twice the width of the mesal. 



Directly or indirectly, the clavicle affords attachment to the Mm. clavo-trapezius, clavo- 

 mastoideus and claco-ddtoicteus, but as it is connected with the sternum and the scapula 

 only by ligaments, it is moved with the muscles instead of forming an efficient fulcrum 

 for their action. 



THE STERNUM (Fig. 7, 30, 50, 72, 73, 99, 100). 

 The sternum or breast bone was briefly described in 210. 



References. Straus-Durckheim, A, I, 496, 497 ; Mivart, B, 49, 50 ; Flower, A, 73 : 

 Humphrey, A, 321-329 ; Gray, A, 207-210 ; Quain, A, I, 25-27 ; Chauveau, A, 75; Chau- 

 veau (Fleming), A, 66 ; Leyh, A, 164-166 ; Parker, A, 215. 



423. Explanation of Fig. 49. The ventral aspect of an adult sternum, with the 

 contiguous parts of the costicartilagines. Incomplete views of the sternum are given in 

 Fig. 30, 50, 72, 73, 99 and 100. 



The sternum consists of a mesal series of osseous or partly cartilaginous segments 

 called sternelrce, united by cartilages. The figure was drawn from a dried sternum, and 

 the intersternebral cartilages are not shown distinctly, neither is indicated the line of junc- 

 tion of the O3S30US and cartilaginous portions of the caudal segment. 



Of the sternebrae, the most cephalic and the most caudal have received special names, 

 prcesternum and yipJiisternum. The intervening segments constitute the mcsosternum. 



424 Mcsosternum. As indicated in 210, there maybe cither 6 or 7 mesosternebrae, 

 making the total number of^sternebrae 8 or 9. The variation is due to the presence or 

 absence of a short and nearly* cubical piece between the xi phi sternum and the sixth con- 

 stant mesosterneber. This piece is neither figured nor described by Mivart (B, Fig. 24), 

 or Parker (A, PI. xxx, Fig. 3), and does not appear distinctly in the figures of Straus- 

 Durckheim (A, PI. vi, Fig. 2, and PI. vii, Fig. 2), notwithstanding his intimation (A, 1,546) 

 that it is always present. In the sterna examined by us this seventh piece is sometimes 

 quite large, and in other cases so small as to be unrecognizable, at least from the surface. 

 We have also observed considerable diversity as to the number of costicartilagines which 

 reach the sternum, but are not yet prepared to say whether 8 or 9 is the more frequent 



