3!S2 PROCEEDINGS OF THE CANADIAN INSTITUTE. 



structures lying above it. The lines of attachment may be under- 

 stood from Fig. 7. 



It is necessary to look more closely at the connections of the 

 malleus. As observed above it articulates in an oblique groove on- 

 the side of the third vertebra. Outside this point its upper surface 

 is connected by ligament with the ventral face of the fourth trans- 

 verse process, and its postero-external angle here passes into the- 

 crescentic ossification (co), which may be described as the posterior 

 sickle-shaped part of the malleus, although it is not developed as a 

 part of the third transverse process. It is in fact an ossification ins 

 the tunica externa of the air-bladder, and only secondarily becomes 

 connected with the third transverse process. A sharp ridge separates 

 these anterior and posterior parts of the malleus. The dorsal and 

 lateral limb of the crescent rests on the ventral face of the fourth 

 transverse process, while its ventral and medial limb rests on a 

 oroove on the sides of the body of the fourth vertebra. 



In the concavity of the crescent, and connected with it in the 

 recent state by fibres of tendinous lustre, is the thickened knob-like 

 end of an oblique ossification (o.o) which is free from the body of 

 the vertebra, but becomes coalesced as it runs backwards and out- 

 wards with the posterior part of the ventral face of the fourth 

 transverse process. Between the body of the vertebra and this 

 oblique ossification is a triangular space in which lies the vena cava 

 inferior. The course of this vessel is ventral to the origin of the 

 third and fourth transverse processes, but dorsal to both the oblique 

 and crescentic ossifications, the intervening space being larger on the 

 right than on the left side to accommodate the larger vessel. 



Across the posterior part of the triangular space described the 

 upper end of the fiat band is attached. All the dorsal median wall 

 of the anterior chamber is likewise firmly bound down to the sides 

 of the bodies of the fourth and fifth vertebrae, and especially to the 

 sharp ridges bounding the aortic canal. Further forwar s also, the 

 dorsal wall is attached to the sharp ridge separating the third and 

 fourth vertebrae by strong fibres to the knob of the oblique ossifica- 

 tion, and to the ventral edge of the thickened anterior part of the 

 fourth transverse process. 



The fibres of the unattached parts of the anterior chamber chiefly 

 converge (1 ) from the anterior wall to the crest separating the anterior 

 and posterior parts of the malleus, and (2) from the rest of the 



