On the specific gravity of different parts of the human brain / by H. Charlton Bastian.

  • Bastian, H. Charlton.
Date:
1865
Catalogue details

Licence: Public Domain Mark

Credit: On the specific gravity of different parts of the human brain / by H. Charlton Bastian. 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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    the temperature of the room, during the fortnight tliat I was working there, varying only from about 71° to 77° Fahr., whilst that of the solutions was about three or four degrees lower than that of the air. The shght increase in the tera])erature of the solutions in these later experiments above that of 60° Fahr., at which all observations upon specific gravity should be conducted, when taken in conjunction, too, with the part compensation afforded by the simultaneous action of the increased temperature upon the bulk of the beads themselves, could produce only a very infinitesimal amount of vitiation in the correctness of the results. And, indeed, seeing that water in its passage through a range of temperature from 32° to 212° Fahr., apparently increases in bulk only by about A- of its original volume, it does not seem hkely, either, that any degree to which the temperature of the solution would fall would exercise a very appre- ciable influence upon the correctness of the observations.* It must be borne in mind that the maximum fall which could have any efiect an hour after tbe ordinary pathological examination, before I could proceed to estimate their specific gravities, and these trays were sometimes wet, I made a few experiments to ascertain what amount of influence, if any, such a length of exposure to air, or contact with a wet tray, would exercise upon the specific gravity of the white and gray matter of the brain, and found that within this period these conditions appeared to exercise no appreciable influence whatever. Thus, white matter, after lying (even completely) in water for a period of thirty minutes, was found to have the same specific gravity as before immersion ; and no change, either, was found in the specific gravity of the gray matter of the convolutions, after allowing portions of tbe brain, covered by the arachnoid, to remain for a similar period with this surface downwards, in contact with a thin stratum of fluid upon a wet tray—-the portions of gray matter examined before and after being taken from what were nearly adjacent portions of the same convolutions. And with regard to the influence of the high summer temperature, no increase of density could be detected after such short periods of exposure, provided the con- volutions were still covered by the arachnoid, whilst as far as the white matter was concerned it was always easy to take portions from beneath a surface which had been at all exposed. Alterations from atmospheric influence were also guarded against, as much as possible, by throwing a towel over the brain during these occasional intervals. * Whilst this paper has been going through the press, I have made some ex- periments in order to ascertain what amount of error can result from inattention to the temperature of solutions, arid have been much pleased to find this so very insignificant when sp. gr. beads are employed, as to render attention to this point of little importance. Thus the compensating variation in the beads is such, that I have found, after adjusting a solution of sulphate of magnesia at a temperature of 60 Falir., to a specific gravity of 1028, the solution could be raised to a tem- perature of 81° Fahr. before the 1'027 bead sank midway in the solution; whilst, on the other hand, when the solution was cooled to 40° Fahr., the deviation was still less, since the 1-029 bead still remained at the bottom of the bottle. During these experiments a thermometer was kept in the solution, and due precautions were taken to prevent alteration in the density of the solution from evaporation. If the solutions, instead of being prepared at the temperature of 60° Fahr., have been adjusted to the beads at a time when the temperature of the weather is above or below this point, a little reflection will show that this of itself tends to diminish the small amount of possible error before alluded to, and so makes attention tn temperature even of less iniportance.