FLEXIBLE BONDS OF UNION AND SUPPORT. 49 



B. 15. Portion of the vertebral column together with part of the 

 skull and pelvis of a Maguari Stork (Euxenura maguan), 

 showing a series of interspinous elastic ligaments. The 

 ligaments extend between the neural spines from the axis 

 to the anterior end of the sacrum. They vary very greatly 

 in size in different regions of the vertebral column ; from 

 the first ligament (3 mm. diameter) they gradually diminish 

 and reach their minimum (1 mm. diameter) between the 

 6th and 9th vertebrae, they then again increase in size and 

 attain their maximum (6 mm.) between the 13th and 17th. 

 From the 17th vertebra onwards the ligaments are divided 

 into a superficial and deep series (Lig. elastica profunda 

 and superficialia) . They increase in size from before back- 

 wards, i. e. from 2 mm. and 3 mm. diameter to 5 mm. and 

 6 mm. respectively. 



Barkow, Syndesmologie der Vogel, 1856, p. 32. 



SUBSPINOUS. 



B. 16. Head and vertebral column of a Sterlet (Adpenser 

 ruthenus) showing a subspinous elastic ligament. The 

 ligament originates at the back of the skull within the mass 

 of cartilage formed by the fusion of the five anterior dorsal 

 arches, and extends from that point to the tail with slight 

 lateral attachments to each arch. It lies throughout its 



O 



course between the upper ends of the dorsal arches, cut off 1 

 by cartilage from the neural canal. A subvertebral elastic 

 ligament is also present, projecting like a " typhlosole " 

 into the lumen of the dorsal aorta ; it extends from the 

 base of the cranium to the tail, and may be considered as 

 a modification of the aortic wall, with function subsidiary 

 to circulation. Black bristles have been inserted between 

 the subspinous ligament and the vertebral column, and 

 blue rods between the subvertebral ligament and vertebral 

 column. 



B. 17. The vertebral column and part of the cranium of a Shad 

 (Clupea alosa), showing two similar elastic ligaments. 

 Though in their general features the ligaments resemble 

 those of the Sterlet, they both show a remarkable develop- 

 ment in the anterior region, the ventral ligament in 



B 



