The nervous system of the American leopard frog, Rana pipiens, compared with that of the European frogs, Rana esculenta and Rana temporaria (fusca) / by Henry H. Donaldson.

  • Donaldson, Henry Herbert, 1857-1938.
Date:
1908
Catalogue details

Licence: In copyright

Credit: The nervous system of the American leopard frog, Rana pipiens, compared with that of the European frogs, Rana esculenta and Rana temporaria (fusca) / by Henry H. Donaldson. 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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    For the foregoing comparison of the central nervous system and its parts, together with the determination of the percentage of water, data on all three species have been available. But before commenting on the results just given, I wish to present some obser- vations based on the comparison of two species only. These additional observations are on the peripheral nervous system and relate first, to the number of medullated fibers in the spinal nerve roots; comparing R. esculenta with R. pipiens (there being no corresponding observations on R. temporaria). Second, to the length of the internodal segments; comparing R. temporaria with R. pipiens (there being no corresponding observations on R. esculenta). The number of medullated nerve fibers in the spinal nerve roots of R. pipiens compared with the number in R. esculenta.—In a female R. pipiens weighing 48.2 grams, Hardesty (’99) reported 14,582^ medullated nerve fibers in both roots of the ten spinal nerves of one side. This was a much larger number than had been found by Birge (’82) in a specimen of R. esculenta of greater body weight. To reduce Birge’s figures for the specimen of R. esculenta, weighing 63 grams, to those for a specimen weighing only 48.2 grams, we have proceeded as follows: The smallest frog in Birge’s series, with a body weight of 1.5 grams, in which he enumerated 2992 motor fibers in the ven- tral spinal roots of one side, was selected as one limit, and to this frog the same proportion of sensory fibers as was found in the 63 gram specimen, was allotted, a concession which probably makes the number of sensory fibers somewhat too large. The number of fibers corresponding to each gram of body weight between 1.5 grams and 63 grams was then determined. By this method, it was found that when the number of fibers in the spinal nerves of the 63 gram frog was reduced to the number for a 48.2 gram frog, it amounted to 92.8 per cent of that found in the 63 gram frog, or 8925 fibers. Thus the difference between the two species is (14,582 — 8925) 5657 fibers, or put in another way, R. esculenta has only about 61 per cent as many medullated nerve fibers in the spinal nerve roots as has R. pipiens. On reducing the original observations of Birge for the number of fibers in the ^ By a clerical error the number was printed on p. 78 (Hardesty ’99) as 14,783. It should be 14,58a, and consequently I shall use the corrected number subsequently, even when referring to Hardesty s paper.