Chemical analysis of the collagen, elastin, and water content of various segments of the internal saphenous vein in the human has been carried out. Normal values were obtained to give a basis for comparison with pathological material from varicosities. The following observations were made: (1) The ratio of connective tissue elements in the internal saphenous vein (ISV) is the reverse of that in the aortic wall; the ISV contains more collagen than elastin. (2) The total scatter of elastin and collagen values in the venous wall is large, mainly due to interindividual differences. No particular dependence on age was observed in the ambulant group. (3) Analysis of neighboring samples of vein in a given individual showed little variation. (4) There was a consistent difference in venous composition in a given individual between the superior segment at the insertion of the ISV into the femoral vein and the inferior segment at the level of the ankle. There was more collagen and elastin superiorly, and more muscle inferiorly. This corresponded to histological analysis showing a thicker layer of circular muscle in the media of the inferior segment. (5) The same differences in elastin content were found in infants who had not yet begun to walk; however, the infant group showed no superior-inferior differences in collagen and muscle composition of the venous wall. It is suggested that this latter difference is a function of upright posture and bipedal locomotion, and the attendant gradient of hydrostatic pressure.

IN 1960 we reported a method of measuring blood flow in individual vessels based on the principle of local thermodilution.1 The present communication presents application of the same principle to measurement of blood flow in the femoral artery in man at rest and during exercise. MethodsAn upstream catheter was used, modified to allow for percutaneous insertion by the Seldinger technic ( fig. 1). Tihe catheter had an asymmetrical double lumen, the narrower lumen being occupied by the leads from the thermistor to an external resistance bridge, the large lumen (1.2 mm.) being used to introduce the catheter over a spiral guide and for injection of indicator. The external diameter was 2.5 mm. The tip of the catheter was slightly conically narrowed and slightly curved. The thermistor was located on the concave surface of the curve (to prevent contact with the vessel wall) about 5 to 10 mm. from the tip. The thermistor was slightly raised from the surface of the catheter, resting on its own lead wires in order to limit a thermal influence on it by the intraluminal contents of the catheter. The insulation layer on the thermistor was as thin as possible in order to have a small time constant, 0.3 second or less, measured in cool water.The indicator was 5 ml. of physiologic saline kept at room temperature. The duration of the injection varied from 0.3 to 0.5 second. Just before each injection we fill the catheter with blood by opening the stopcock slightly. This allows us to subtract a precise dead space of the catheter from the known total injectate. Flow is calculated by the arterial formula: m * 60 * r/t, -tt/ * 1.08 F~~~~A * f where F =flow in ml./min., mamount of injectate, corrected for dead space, r = registra-From the Institute for Cardiovascular Research, Prague, Budejovicka', Czechoslovakia. 86 tion paper speed in mm./sec., tBblood temperature in degrees C., and tlindicator temperature in degrees C., A = area under the thermodilution curve in mm.2, and f = degree of temperature change corresponding to 1 mm. of deflection on the registration paper. Other details have already been described.1The terminal part of the dilution curve may be distorted by cooling of the thermistor from the intraluminal contents, and this is manifest as a delayed return to baseline ( fig. 2). This source of error can be removed by extrapolating the exponential decay of the curve from two points (0 and P) previous to the distortion, and the integral area (A) integrated from 0 to infinity:where A2area under extrapolated curve from 0 to infinity in mm.2, y1 = distance in mm. of 0 to baseline, Y2 =distance in mm. of P to the baseline, t2-t1 time difference between 0 and P in mm., and 0.4343 = log e. Area A1, crosshatched, is determined planimetrically.The accuracy of the results was tested by model experiments where total flow was known from a rotameter, with use of 8-mm. tubing, which approximates the lumen of the femoral artery in the inguinal region. Figure 3 shows the degree of agreement between the two methods over the range 240 to 3,82...

In the past, increased attention was given to the development of an optimal shape for the inlet part of LP turbine casings in SKODA POWER. A double-flow design is typically used for high power output turbines. An optimized shape for the internal diffuser has been found, which transforms the kinetic energy of steam into increased pressure, thus effectively increasing the thermodynamic efficiency of the stage. Some conclusions have been drawn from laboratory experiments, others derived directly from on-site measurements at power plants. The conclusions from the development of double-flow turbines form the basis for the design of the single-flow turbine arrangement. Single-flow design is typically used for lower output turbines. There are still some limitations in applying this arrangement. The designer needs to resolve the bearing position and how to ensure access to them. Reinforcing the ribs and supports are used, therefore, to ensure the rigidity of the entire casing. The optimization of the single-flow diffuser shape is therefore the subject of the study presented below.

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