Licence: Public Domain Mark
Credit: Structure and functions of the brain and spinal cord. Source: Wellcome Collection.
Provider: This material has been provided by the Augustus C. Long Health Sciences Library at Columbia University and Columbia University Libraries/Information Services, through the Medical Heritage Library. The original may be consulted at the the Augustus C. Long Health Sciences Library at Columbia University and Columbia University.
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![have to say upon the particular points in the structure of the spinal cord of the bird and the cat, before discussing this connection, since it has ])een much more elucidated by investigation of the higher than of the lower vertebrates. The spinal cord of the Ijird requires no special description. The canal which penetrates it, however, opens at the lowest part in the lumbar enlargement, just like the fourth ventricle in the highest part, or medulla oblongata. This lower opening is known as the rhomboidal sinus. Similarly, the spinal cord of the cat (see Fig, i), as an example of general plan of structure in the carnivora, is merely a multiplication of the simple forms, and, consequently, Avhen Ave examine the cord in the carnivorous animal, we only see a more complex arrangement of fibres and cells than what we discover in the frog-. This com- plication does become of interest and importance, however, when we finally explain the arrangement of the spinal cord as \ve see it in man ; but we must first turn again, putting that aside, to the condition of affairs in the frog. We do not know absolutely the course of the fibres as they enter the frog's cord by a sensitive or afferent channel, and we can only suppose that they are partly direct, partly indirect. We do know, however, that the nerve cells (jr](https://iiif.wellcomecollection.org/image/b21218262_0110.jp2/full/800%2C/0/default.jpg)
