The pyramidal tract in the cat, dog and monkey / by Sutherland Simpson.

  • Simpson, Sutherland, 1863-1926.
Date:
[1906?]
Catalogue details

Licence: In copyright

Credit: The pyramidal tract in the cat, dog and monkey / by Sutherland Simpson. Source: Wellcome Collection.

Provider: This material has been provided by The Royal College of Surgeons of England. The original may be consulted at The Royal College of Surgeons of England.

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    supposed to be. It included continuously the whole length of the precentral or ascending frontal convolution, but did not extend at any point behind the fissure of Eolando, so that this fissure would seem to mark a physiological as well as an anatomical division of the brain. On the mesial surface of the hemisphere also the motor area was found to extend downwards for a shorter distance than was expected,—it did not reach the calloso-marginal fissure. In a few cases also, chiefly in America (12, 13, 14, 15, 16), the human brain has been proved to be directly excitable by electrical stimulation. In these cases the areas under observa- tion were necessarily limited, but in the main they have been found to correspond with those mapped out on the brain of the monkey. We must next consider the path pursued by the fibres which carry the impulses from the cells situated in the motor cortex to the cells of origin of the cranial motor nerves and of the anterior spinal nerve roots, that is to say, the fibres which to- gether make up the pyramidal tract. Several methods have been employed for investigating the course of these fibres, but the two most important may be said to be the embryological method of Ftechsig and the Wallerian method or method of secondary degeneration. As the latter has been used exclusively in the present research, it may be well to review briefly the work done by previous observers and the results they have obtained by this method. The Degeneration Method was first in the field, and has prob- ably been more fruitful than any other in advancing our knowledge of this subject. It depends upon the fact, first dis- covered by Dr Waller (17) of London about the year 1850, that when a nerve fibre is cut off from that part of its cell of origin containing the nucleus, it undergoes degeneration. Any lesion in the brain or spinal cord which so cuts off a fibre or tract of fibres leads to a degeneration of that fibre or tract of fibres,— descending if the cell be above the lesion, ascending if the cell be below it. Such a lesion may be produced experimentally on one of the lower animals amesthetised, or it may occur in the human subject as the result of accident or disease. By certain methods of staining, which will be given in detail subsequently,