Skeletal changes affecting the nervous system produced in young dogs by diets deficient in vitamin A / by Edward Mellanby.

  • Mellanby, Edward, Sir, 1884-1955.
Date:
[1941?]
Catalogue details

Licence: In copyright

Credit: Skeletal changes affecting the nervous system produced in young dogs by diets deficient in vitamin A / by Edward Mellanby. Source: Wellcome Collection.

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    animal, i.e. the vertebrae are not generally larger but are only locally thickened; (2) that the area of the lateral portions of the vertebra is increased in the - A dog; (3) that the main change in the - A dog is the reduction in space between the dura and the bone and to a less extent between the spinal cord and the dura. Examination shows that one reason for the reduction in size of the spinal canal is the inward growth of the lateral mass of the vertebra, thus encroaching on the spinal canal. The change in position of the vertebral artery and vein relative to the body of the vertebrae can also be seen. In the - A animal (PI. V, fig. 66) these vessels are placed more dorsally in relation to the intervertebral disc than those in the + A animal (PI. V, fig. 6a). As regards the space surrounding the spinal cord, it will be seen that (1) the reduction of the space between the dura mater and the cord is general but is greater on its ventral side, and the slight swelling in this position in the normal animal (PI. V, fig. 6a) is absent from the —A animal (PI. V, fig. 66); (2) there is a great reduction in the size of the spaces between the body and the wings of the vertebrae for the passage of the spinal nerves. In fact, on the left side of the -A dog (PI. V, fig. 66) compression of these nerves and especially of the posterior root ganglion can be seen between the wings and the body of the vertebra: this state of compression, in comparison with the free space occupied by the corresponding nerves and ganglion in the normal animal, can be better appreciated in PI. VI, figs. 7 a and 76, which are higher power photomicrographs. There is also some lengthening of the spinal nerves during this passage through the spinal canal of —A dogs, because the nerve roots pass more obliquely across the canal towards the periphery than in the +A animals. The pressure exerted by the bones on the spinal nerves and the posterior root ganglion in the animals fed on vitamin A deficient diets is undoubtedly largely responsible for the degenerative changes previously described in these nerves [Mellanby, 1933, 1934, 1935], although at the time this was not appreciated. Attention, however, was drawn to what at that time seemed a curious fact, namely, that the anterior roots in the spinal canal central to the posterior root ganglia generally escaped degenerative changes, whereas the nerve fibres of the posterior roots in the same position were often degenerate. The reason for this difference in distribution of nerve degeneration now seems clearer. The nerve cells of the posterior root ganglion are often damaged by the effects of pressure and their axis cylinders, both peripheral and central to the ganglion,