The APS Journal Legacy Content is the corpus of 100 years of historical scientific research from the American Physiological Society research journals. This package goes back to the first issue of each of the APS journals including the American Journal of Physiology, first published in 1898. The full text scanned images of the printed pages are easily searchable. Downloads quickly in PDF format.

643is equal to the rate at which the volume of blood in the flask diminishes. To convert the deflection of the light beam, in mm, to volume of blood, in ml, a known volume of blood is introduced from a buret into the flask being weighed, and the resulting deflection is recorded after each registration.In the experiment depicted in Fig. 3, a recording balance was employed which had the following characteristics. The flat spring (S, Fig. 1) was 45 mm in length, and had an elasticity of 80 g/mm. A 350 cc side-arm flask, weighing 180 g, was used as the blood reservoir. This flask was suspended from the lever arm (L) at a distance of 48 cm from the fulcrum (F). The total length of the lever arm was 57 cm. For the registration of pressure, the camera had to be situated just 2 A t from the optical manometers. However, by interposing 3 vertically-oriented plane mirrors at suitable locations between the second oblique plane mirror (M2, Fig. 2) and the camera aperture (A) it was possible to employ an optical distance of 18.3 M for the recording balance. The lamp filament (FIL) was focused at the aperture by means of a 20-power telescope. Under these conditions, the loss of 1 ml of blood from the flask resulted in a beam deflection at the aperture of 4.33 mm. Since the slope of the flow curve (Q) in Fig. 3 is 7.85 mm/sec, this represents an arterial inflow of 1.81 ml/sec, at an arterial pressure (Pa) of 94 mm Hg, and a venous pressure (Pv) of 3 mm Hg. The natural frequency of the recording balance, with the flask filled with blood, was 9.5 cycles/sec. When the flask was almost empty, the frequency increased to 12.2 cycles/sec. The sensitivity remained constant over this entire range of weight. Summary.A sensitive mechanical balance is described which records optically the stress exerted upon a flat spring. By means of 2 obliquely oriented plane mirrors, a vertically directed strain upon the spring is registered as a horizontal deflection of a line of light a t the camera aperture. The sensitivity and frequency may be varied readily to meet changing requirements. An example is described to demonstrate how the balance may be employed as a flowmeter in perfusion studies upon isolated tissues.

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