ANATOMY OF MEG AFTER A LONGIMANA. 75 



the 8th vertebra, and back to four or five from the end, there is 

 a continuous hsemal ridge, most projecting at the middle, giving 

 the vertebra, on side view, a convex outline below. 



After the 1st caudal, the hernial groove, or fossa, is concave 

 longitudinally as well as transversely, owing to the rise of the 

 tubercles. In width it increases from 2 to 2| inches at the 

 middle, where it is widest, and is about 4 inch in depth. Here 

 two nutritious foramina pierce the bone, about goose-quill size, 

 one on each side, f to 1 inch apart. On the 7th the hsemal 

 groove is in length 4 inches ; in breadth, in front 3 inches, pos- 

 teriorly 2 inches; in depth 1| inches. It now assumes a more 

 oval form, and on the 10th (the last chevron vertebra) it is in 

 length 4 inches, in breadth 2|, in depth 1 J ; the nutritious fora- 

 mina close together ; the openings of the vertical passages, in 

 the roof, about 1 inch apart. On the 11th, the long axis of 

 the oval is still antcro-posterior, 2 to 2^ inches long. If broad, 

 and I inch deep. The septum between the mouths of the ver- 

 tical passages is contracted to f inch. Behind the 11th, the 

 haemal fossa becomes oval transversely, and the two great aper- 

 tures become gradually more separated. On the 12th, the fossa 

 is broader than long, the great apertures f inch apart. On the 

 14th, the length of the fossa is 2 inches, the breadth 2J inches, 

 the distance between the two great apertures 1| inch. After 

 the 15th, the fossa becomes broadly diamond-shaped. After the 

 14th, the distance between the apertures of the vertical pas- 

 sages diminishes actually, but not in proportion to the lessened 

 size of the bones. At the 18th vertebra they are still f inch 

 apart, the fossa 2 inches broad, the length ^ inch less. After 

 the 11th, the two nutritious foramina are transferred from be- 

 tween the great apertures to behind them, and continue so after 

 the septum between the great apertures has regained breadth. 



9. Vertical Passage and Foramina. — This large passage, 

 present in the middle and posterior caudal regions, establishes, 

 when complete, a communication between the hsemal and neural 

 canals. In some of the posterior caudal vertebra it is a simple 

 vertical canal; in front, as in the 7th caudal (the 12th or 13th 

 of B. musculus, the 9th of B. borealis), it occurs as a series of 

 three perforations (4 foramina) in the vertebra, on each side. 

 On its way from the hsemal to the neural canal three stages 



