78 PROFESSOR STRUTHERS, 



roundabout groove. On the seven posterior (behind the 14th) 

 the neural perforation ceases. A median septum rises to the 

 level of the edges of the vertebra, separating the funnel-like 

 fossae into which the passages open, and on each side of the 

 septum nutritious foramina are seen, crow-quill to goose-quill 

 size. In the four previous vertebra? (11th, 12th, 13th, 14th) 

 these nutritious foramina are gathered together into a larger 

 central one in the groove or pit which represents the opened- 

 out neural canal. ^ 



Meaning of the Vertical Passage aiul of its various Con- 

 ditions. — In endeavouring to find an explanation of the different 

 arrangement of the vertical passage and its foramina along the 

 region, it is observed that the passage is within the body of the 

 vertebra where there are no transverse processes. Also that, 

 with this roofing-over of the passage, the side of the body is 

 nearly filled up, or (as on the 11th, 12th, and 13th) even con- 

 vex ; and that the excavation of the side of the vertebral body 

 begins on the 7th and 6th, as we go forward. If the hinder 

 vertebrae are taken as the type, Avith the passage concealed in 

 the bone, the commencing excavation on the 7th and 6th 

 would explain the imroofing of the upper and lower parts of 

 the middle stage on these vertebrae and the entire opening up 

 of it on the 5th. Or, going backwards, we perceive that, on 

 the anterior four caudal vertebrae, the segmental blood-vessels 

 do not mark the bone at all, that they begin to groove the 

 bone on the .5th, to pierce it gradually on the 6th and 7th, 

 with disajjpearing transverse processes, and, after the 7th, to 

 become covered by a bony roof. The adaptation may thus be 



^ Size of the Foramina of the Vertical Passage. — The size of the apertures of 

 the second stage does not go in proportion to that of the vertebrse. They receive 

 the point of the fore-tinger, oval antero-posteriorly, with almost no iliminution 

 hack to the 10th. The next three are encroached on a little by the broad low 

 pedicles. In the 14th and 15th they have become round and receive the ring- 

 finger above (diameter /^ inch), the fore-finger below. In the 16th they are large 

 enough above to receive the point of the little finger. In the 17th and back- 

 wards they are oval transversely. They are always wider below than above. The 

 perforation of tlie luemal ridge of the 7th admits the thumb, of the 6th the fore- 

 linger. The perforation of the neural arch of the 7th admits the point of the 

 fore-finger ; of the 8th and 9th, the point of the little finger ; of the succeeding 

 vertebrae (10th to 14th) less. These are present on one side only, as above 

 noted, but the neighbouring aperture of the second stage is not larger on the side 

 which possesses a neural perforation than on the side which does not. 



