THE HUMAN STERNUM 29 



scrutiny of fifty-three cases of fusion of presternum and niesosternum 

 shows in twenty-one the existence of what appears to be an articular hicct 

 for the first costal cartilage, instead of the usual excavation. One hesitates 

 to speak more confidently in regard to this point without further iiivcstii^a- 

 tion upon sterna in a fresh condition. All my specimens were dry and 

 macerated ; hut the conditions were striking- enough to warrant the sn - 

 gestion that just as separation of the presternum and mcsostenunn is 

 associated with fusion of the first costal cartila^^c with tlie presternum, so in 

 cases of fusion of these two elements of the sternum, an arthpHli;il articula- 

 tion may coincidentally occur between the sternum and tlic first costal 

 cartilage so as to permit free movement of tlie ribs and ex[>ansion df tlie 

 chest. 



Although MusGROv !■:,*' among eighteen examples of CMSto-sternal 

 joints, never found a single case of a diarthr'),lial joint bet^,een the lirst 

 costal cartilage and the presternum, Anthony,' out of sixty-six cases, f )und 

 such a joint in seven examples, of which five were bilateral. He quotes 

 TcHAUssow as recording nineteen examples out of eighty cases. 



Fusion of the First Piece of the Mesosternum only with the Frcsiernuni. 



This rare condition illustrates the fact that fusion of the iiiesosternum 

 with the presternum is not dependent upon age alone. y\s alreaJ\- statcei 

 (p. 20), in one foetal sternum the fibrous septum of separation of tiie 

 cartilaginous presternum and mesosternum was situa<ed opposite ihe 

 attachment of the third costal cartilages. There is, t!ierefi)re, a possibility 

 at least that all cases of this sort may he congenital in origin. Among- the 

 sterna in my possession there are five in which the first piece of the meso- 

 sternum is separate from the otlier pieces, and fused with the presternLun. 

 The ages of the sterna were eighteen, nineteen, twenty-five, forty-tour, and 

 fifty-nine years* (PI. VI, Fig. 41). Dwigiit"'* has elescribed an example of 

 this condition, and Turner'^ has given a case occurring in the skeleton of 

 an Andaman islander. 



In the gibbon it is the normal condition, as described by de Blain- 

 viLL!<,* KiiiTH, and others. 



* Aijollui- cxiimple, not Included abcjve, occurs along with other skeletal peculiarities in the skeleton 

 of an African negro, aged twenty years, in the anatomical museum of this University.^ ^ 



