AORTIC LIGAMENT IN INDIAN FISHES. 75 



Plate II. 



Fig. 7. A diagrammatic longitudinal representation of the position of the ligament 

 inside the dorsal aorta in Wallago attu. The lateral wall of the aorta 

 has been removed to show the position of the ligament, lig., aortic 

 ligament ; stis.f., suspensory fold ; 3rd v., third vertebra ; 2ncl v., second 

 vercebra; 1st v., first vertebra; Afl.o., basioccipital; d.tv.a., dors^al wall 

 of aorta ; v.w.a., ventral wall of aorta : lig.per., the place v.-here the 

 ligment perforates through the dorsal wall of the aorta and becomes 

 attached to the bone; cav.a., cavity of aorta; lig.a.', anterior branch of 

 the ligament running through the wall of the aorta ; lig.a.", the place 

 wliere the anterior branch of the ligament perforates through the most 

 anterior dorsal wall of the aorta ; lig.a.'", the anterior branch of the 

 ligament after it comes out of the aorta and runs beneath the basioccipital 

 bone ; eff.a., efferent arteries. 



Fig. 8. Transverse section through the aorta of Wallago attu in the region where 

 the ligament perforates through the dorsal wall of the aorta. This section 

 is supposed to have passed through A-B region of fig. 7 (X 18). c.aor., 

 cavity of aorta; d.w.a., dorsal wall of aorta; lig.per., the place where the 

 ligament perforates through the dorsal wall of the aorta and becomes 

 attached to the bone. 



Fig. 9. Transverse section through C-D region of fig. 7. The ligament {lig.) here 

 runs through the upper region of the dorsal wall of the aorta (X 18). 

 Lettering as in fig. 8. 



Fig. 10. Transverse section through E-F region of fig. 7. The ligament here 

 runs through the lower region of the dorsal wall of the aorta (X 18). 

 Lettering as in fig. 8. 



Fig. 11. Transverse section through G-H region of fig. 7 (X 35). d., adventitia ; 

 c, cartilaginous tissue ; h., media ; i7it., intima ; a., elastic fibres ; lig,, 

 ligament ; him., bundles of elastic fibres. 



Fig. 12. Transverse section through I-J region of fig. 7. A slight proliferation 

 takes place inside the cavit}' of the aorta in the region where the ligament 

 is situated (X 16). car.c, cartilage-cells ; ?/^., ligament ; cZ.iy..^., dorsal 

 wall of aorta. 



Fig. 13. Transverse section through K-L region of fig. 7. The proliferation of the 

 dorsal wall of the aorta containing the ligament grows deeper (X 18). 

 Lettering as in fig. 8. 



Fig. 14. Transverse section through M-N region of fig. 7. The proliferation reaches 

 nearly its maximum and the ligament acquires its characteristic shape. 

 Posteriorly the ligament flattens out, being narrower dorso-ventrally than 

 from side to side (X 18). Lettering as in fig. 8. 



