. Elements of human physiology. Physiology. THE A'ASCULAR MECHANISM 3 99 of the bulb of the enema. The tiuid in passmg from (a) to (v) has now practically no resistance to overcome, and accordingly we find the pressm-e-tracings of the two manometers (Fig. 101) are almost identical, the fluid escaping from the end of (v) at each stroke of the pump. c' is now clamped so that all the fluid must pass through the tube (c'-) with a high resistance. Tracings are again taken (Fig. 102), and they show that the pressure on the arterial side at first rises with every beat till it has attained a Fig. 102.
. Elements of human physiology. Physiology. THE A'ASCULAR MECHANISM 3 99 of the bulb of the enema. The tiuid in passmg from (a) to (v) has now practically no resistance to overcome, and accordingly we find the pressm-e-tracings of the two manometers (Fig. 101) are almost identical, the fluid escaping from the end of (v) at each stroke of the pump. c' is now clamped so that all the fluid must pass through the tube (c'-) with a high resistance. Tracings are again taken (Fig. 102), and they show that the pressure on the arterial side at first rises with every beat till it has attained a Fig. Tracing from artificial schema with considerable peripheral resistance, a, arterial; v, venous manometer. certain height, where it remains stationary, merely oscillating with every stroke of the pump. The venous manometer, on the other hand, shows scarcely any rise of pressure, and its oscillations become less and less till they disappear, and the flow becomes continuous. There is one feature in the circulation which is not represented in the above schema. In the latter the system of tubes is open at both ends, and the amount of fluid supplied to the contracting heart-model is constant. In this model therefore, so long as the resistance in the circuit is constant, the pressure in all parts of the circuit will vary directly with the force of the heart-beat, and a rise of arterial pressure will be attended with a smaller rise of venous pressure, as shown in Fig. 102. In the body however the blood- vessels form a closed circuit, containing a certain invariable quantity of fluid. We may imitate this condition in the schema by connecting the venous end of the tube with the supply-tube of the enema syi'inge, having previously over-. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Starling, Ernest Henry, 1866-192
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