The anatomy of the vertebral column in serpentes

Abstract

The author has made an intensive study ot the morphology of snake vertebrae by a careful examination of whole preparations stained with alizarin and of transverse, frontal and sagittal sections. The more important features discovered are as follows: (1) The already recognized regions,precaudal andcaudal, of the ophidian vertebral column may be further divided into several sub-regions;viz., thecervical, thoracic, lumbar, antero- caudal, mid- caudal andposterocaudal sub-regions. The characteristics of each sub-region are dealt with. (2) The general structure of the trunk vertebra in Serpentes is described in detail. Amongst the new features discovered may be mentioned the presence of a lateral projection on each side of the prezygapophysis which serves for the attachment of certain muscles and appears to correspond to theprocessus mammillaris of mammals, the differences in the extent and configuration of theprocessus spinosus; the occurrence of two pairs of intervertebral foramina (superior intervertebral and inferior intervertebral) on each side of the vertebral column and a pair ofintravertebral sub- central foramina. (3) The trunk vertebrae ofEryx johni have been studied in minute detail by means of serial sections. The precise relation of contiguous vertebrae, as well as the nature of intervertebral and vertebro-costal articulations, is described. The supra-central ridge, two supra-central cavities, and the disposition of the marrow-spaces are described for the first time. (4) The minute anatomy of the trunk vertebrae ofPtyas mucosus. Lycodon aulicus, Typhlops braminus andEnhydrina schistosa has been investigated. It is found that the configuration of the vertebra, the structure of the processus spinosus, the disposition of the marrow-spaces, the extent of the arching of one vertebra over another, the zygapophysial and zygosphenal articulations, and the occurrence (or otherwise) of the hypocentrum vary from species to species. (5) The minute anatomy of the caudal vertebrae ofLycodon aulicus,Natrix piscator, andEnhydrina schistosa has been dealt with and the differences between the various sub-caudal regions described.