504 Mr. L. F. Vernon-Harcourt. 



vertebral disks, the measurements were made along the axial line of 

 the column. The spines were divided in the mesial plane when 

 thoroughly frozen, so that there was no reduction in the depth of the 

 cartilaginous disks through the bulging out of their central soft 

 portions. In the European we find the largest proportion of carti- 

 lage in the construction of the lumbar region. In four female spines 

 the average was found to be 35*7 per cent, cartilage to 64'3 per cent, 

 bone.* In the Australian the amount of cartilage is reduced in con- 

 formity with the lengthening of the vertebral bodies ; the proportion 

 is 30'6 per cent, cartilage to 69 '4 per cent. bone. In the Apes, a still 

 further reduction in the amount of cartilage is manifested ; even in 

 the Orang with vertebrce proportionally as short as those of a 

 European, the amount of cartilage in the lumbar part of the spine is 

 relatively much less, viz., in the European 35'7 per cent., and in the 

 Orang 27 per cent. In the Chimpanzee, the marked fall :in the 

 amount of cartilage is in a measure due to the extremely thin disk 

 which intervenes between the last lumbar vertebra and the base of 

 the sacrum. 



In the erect attitude of Man the greater amount of cartilage lessens 

 the shocks transmitted upwards through the column. In the prone 

 or semi-prone position of the trunk the same provision is not so 

 necessary. 



" The Principles of training Rivers through Tidal Estuaries, 

 as illustrated by Investigations into the Methods of 

 improving the Navigation Channels of the Estuary of the 

 Seine." By LEVESON FRANCIS VERNON-HARCOURT, M.A., 

 M.Inst.C.E. Communicated by A. G. YERNON-HARCOURT, 

 F.R.S. Received January 19, Read February 7, 1889. 



(PLATES 24.) 



The conditions affecting the training of rivers in the non-tidal 

 portions of their course by jetties, or rubble embankments designated 

 as training walls, are well understood. Training walls substitute a 

 straightened uniform channel for irregularities and varying widths, 

 improving the flow of the current and rendering it uniform, so that 

 scour occurs in the shallow, narrowed portions, and more uniformity 



* Aeby gives the proportion of bone and cartilage in the different regions of the 

 European spine at different ages, but as he measured the front aspect only of the 

 vertebrae and disks, his results cannot be compared with the above. In front and 

 behind the vertical diameters of the disks and vertebral bodies are modified by the 

 spinal curvatures. To obtain the most accurate information regarding the relative 

 proportion of bone and cartilage in a region, the different elements should un- 

 doubtedly be measured along the axial curve. 



