On the percentage of water in the brain and in the spinal cord of the albino rat / by Henry H. Donaldson.

  • Henry Herbert Donaldson
Date:
1910
Catalogue details

Licence: In copyright

Credit: On the percentage of water in the brain and in the spinal cord of the albino rat / 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 brain, the records show in both sexes ranges in the per- centage of water in the different age groups as follows AGE PERCENTAGES 0-10 days total range 3 units 86-89 10-20 days . total range 5 units 82-87 From 20 to 100 days the range diminishes, and after this latter age it does not amount to more than one unit. The ranges for the spinal cord are less than those for the brain. It will naturally be asked whether among individuals belonging to the same litter, reared under similar conditions and killed at exactly the same age there is any difference in the percentage of water between those having relatively heavy brains and spinal cords and those in which these organs are relatively light. This question seems to be answered in the negative by the result of 25 pairs of observations recently made. The figures are as follows:— PER CENT PERCENT OF WATER OF WATER Heavy brains 78.651 72.436 Heavy cords Light brains 78.649 72.465 ’ Light cords In both instances as is seen, the differences found are too small to be significant. It may be added that the weight of the light brains was about 96 per cent that of the heavy, and similarly the weight of the corresponding light spinal cords about 93 per cent. Such differences as we find therefore among specimens of the same age must depend on some other cause than the individ- ual variations in the weight of the central nervous system. I feel sure that the irregularities seen in the curve for the cord, chart 2, 95-115 days, are purely incidental and would not appear on repeating the observations. At the same time it is seen that the percentage of water in the female spinal cord after the period of rapid growth, is in general a trifle higher than in the male. This is an unexpected result. The mean difference as determined from those entries in table 2 where there are data for both sexes at a given age (i. e., up to 230-240 days) is 0.36 per cent. At the moment this difference is most readily explained as one effect of the passive lengthening
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