SOME MORPHOLOGICAL FEATURES OF THE SPINAL CORD IN THE RABBIT, WITH SPECIAL REFERENCE TO THE PRODUCTION OF ARTIFACTS

Abstract

1. The occurrence of artifacts in the spinal cord of the rabbit as exposed by the usual post‐mortem methods is described. Such artifacts were not met with in the spinal cords of rat, guinea‐pig, cat, dog, goat, or monkey, exposed in the same way. The artifacts occurred principally in the upper thoracic and upper lumbar regions, and were of two varieties— (A) Large discrete swellings on the posterior surface of the cord associated with large underlying cavities. This artifact was due to spontaneous herniation of cord substance through small accidental tears in the dura mater. The spontaneous herniation was shown to be the combined result of three morphological features of the exposed cord and meninges in the rabbit, namely (i) The posterior part of the dura is tightly stretched (mainly longitudinally) and exerts a direct pressure on the posterior surface of the cord, the subarachnoid space in this region being obliterated. (ii) In the upper part of the spinal cord this dural pressure is accentuated by the usual flexed attitude of the upper part of the vertebral column at post‐mortem examination. (iii) In those two regions of the cord where the artifacts most commonly occur the cord substance is softer in consistence than elsewhere. Serial sections of the cord revealed quantitative differences in the proportions of the white matter, myelin, neuroglia, and pia mater at different levels which might account for the softer consistence in these two regions. The rabbit's cord as a whole appeared to be softer than that of other species. (B) Multiple small radial cavities or cracks in the cord substance. These were shown to result from the exposure of the cord and to be related to the soft consistence of the cord, but their precise cause was not determined. 2. Methods are described for histological fixation of the cord without opening the vertebral canal, by which means the above artifacts can be eliminated. 3. Mention is made of the varying size of the central canal at different levels in the rabbit's cord. 4. The frequent occurrence of a few small spherical empty holes in the white matter of the rabbit's brain and spinal cord is reported. Their nature is discussed, but no conclusion is reached as to their significance. 5. The possible occurrence of similar artifacts in other species is discussed and the importance of eliminating such artifacts in all pathological investigations of acute traumatic lesions of the spinal cord is pointed out. I have to thank the Carnegie Trust for the Universities of Scotland for a grant towards the cost of the illustrations of this paper. © 1943 The Physiological Society