Retrograde degeneration in the spinal nerves.

  • Ranson, Stephen Walter, 1880-1942.
Date:
1905
Catalogue details

Licence: Public Domain Mark

Credit: Retrograde degeneration in the spinal nerves. 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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    It is also important to note that the number of medullated dorsal root fibers is constantly increasing in the growing animal (Hatai *02). In the second cervical root of the white rat at twelve days of age the number of medullated fibers is less than that given in Table II, which represents the number in rats seventy-two days old. In two rats twelve days old thenumberof medullated dorsal root fibers was found to be 1608 and 1521, respectively. Hence, when the nerve is cut in animals of this age, even fewer medullated fibers are injured than would be the case in the adult animal. It should also be mentioned that the number of dorsal root fibers may be taken as a fair indication of the number of afferent fibers in the peripheral nerve, the distal excess (Hardesty '05) not being very large in this nerve of the rat. Table III shows that the ventral and dorsal rami of the nerve contain only 8 percent, or 10 per cent, more fibers than are found in the ventral and dorsal roots. It is, therefore, not misleading to use the number of dorsal root fibers as an index of the afferent fibers in the peripheral nerve. TABLE III. Showing the Distal Excess in the II C. Nerve of the Adult White Rat. Weight. Ventral Root. Dorsal Root. Sum of Roots. Distal Excess. Percentage of D. E. Sum of Rami. Ventral Ramus. Dorsal Ramus. 302 gms. 161 gms. 646 672 2,386 2,090 3,032 2,762 257 276 8 10 3,289 3,098 887 708 2,402 2,390 The present studies were carried out on white rats in which the second cervical nerve of the right side had been divided. Sonic-animals, operated on when twelve days old, were allowed to live for two months, others for four months; the nerve was also cut in adult rats which were allowed to survive the operation four months. A numerical analysis was then made of the spinal gan- glion and of the ventral and dorsal roots of the injured nerves, in order to determine to what extent degenerative changes had taken place and what amount of repair, if any, had occurred. Technique.—In operating upon white rats twelve days of age it is necessary to work rapidly and to conserve, as far as possible, the body temperature. The little rat was held in position in the hands ol an assistant with its neck slightly stretched and head bent forward. An incision was made- in the midline on the- back ot tin neck, with the atlas at its middle point, and carried down-