File:American journal of physiology (1898) (14595650159).jpg

Identifier: americanjourn01ameruoft (find matches)
Title: American journal of physiology
Year: 1898 (1890s)
Authors: American Physiological Society (1887- ) American Physiological Society (1887- ). Abstracts of papers presented at the fall meeting American Physiological Society (1887- ). Proceedings
Subjects: Physiology Physiology
Publisher: (Bethesda, Md., etc.) American Physiological Society (etc.)
Contributing Library: Gerstein - University of Toronto
Digitizing Sponsor: University of Toronto

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Fig. I. Record of venous outflow from brain under arterial pressures of 60 mm.,380 mm., and 60 mm. Under 60 mm. Hg. the outflow = 18.13 c.c. per min. 380 = 102.66 Return to 60 = 10.24 The time record at the top of the illustration is in seconds. It is evident from the data given that in all the experiments made,the blood-flow through the brain diminished as the experiment pro-ceeded, and this effect was most marked after the blood vessels hadbeen submitted to very high pressures. The probable explanation ofthis fact is that the dead capillary walls permitted a rapid filtrationof liquid, which rendered the brain oedematous. This condition, in- High Arterial Pressures upon the Blooei-flow. 63 deed, was apparent to the eye when the brain was exposed aftersubmission to the high intravascular pressures. This variation fromnormal conditions does not, however, affect the value of the experi-ments so far as the main point under investigation is concerned. The
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Fig. 2. Record of venous outflow from brain under arterial pressures of 60 mm. and460 mm. (2d experiment.) Under 60 mm. Hg. the outflows 1.74 c.c. per min. 460 = 252.72 The irregularity in the beginning of the curve showing the outflow under 460 mmarterial pressure, is owing to a stoppage of the drum, as will be seen by consulting thetmie-record above it. ° 64 W, H. Howell. brain was still in the unopened cranium, and the physical conditions,which have been supposed to cause a compression of the veins and atemporary or permanent slowing of the blood-flow when the arterialpressure is suddenly raised to supra-normal levels, still prevailed.Indeed, the oedematous condition of the brain should have exag-gerated this effect instead of ■ counteracting it. Nevertheless,the records show that in all cases where the arterial pressure wassuddenly raised to as much as 400 or 500 mm. of mercury, theoutflow of blood from the cerebral veins increased promptly, andthere was no indication at all of

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