The object of this Communication was to demonstrate two rheological properties of cervical secretion, namely, flow-elasticity and Spinnbarkeit. There is evidence that these properties undergo cyclic variation during the menstrual cycle and bear relation to ovulation, to penetrability by spermatozoa and to pregnancy. By means of the menstroscope, designed by Scott Blair, flow-elasticity or elastic recoil can be measured. It is found to be most marked at the time of ovulation when also the mucus is thin and transparent. Spinnbarkeit—the capacity of liquids to be drawn into threads—is also capable of accurate measurement by drawing away a coverslip placed on a blob of mucus which is drawn out into a long thread. It is also more marked at the time of ovulation and is almost absent in pregnancy. Plasticity and tack, two further properties of cervical mucus, were also discussed. It is believed that these tests will prove to be of value in diagnosis of ovulation and in the study of sterility.
The cyclical changes in the flow properties of human cervical mucus during the menstrual cycle, and the formation of the quasi-solid cervical plug during pregnancy have been investigated subjectively during recent years. Quantitative measurements have, however, been hampered by the inadequacy of the experimental techniques available.Clift (1945) made use of an instrument (the Scott Blair menstroscope) which gave an approximate measure of a specific elastic property of the mucus. A column was partially extruded from a capillary under air pressure, which was suddenly released. The distance the meniscus returned into the capillary was measured, and was shown to vary with the time in the menstrual cycle.In a note, Clift, Glover & Scott Blair (1950) described a viscometer which by an ingeniously simple air pressure system emptied a capillary at constant speed. The machine was not altogether satisfactory in use, and the work has been repeated, using a new viscometer as improved by Scott Blair, but with a fundamental difference in technique.
METHODSThe Rheometer The instrument, generously purchased for this work by Ortho Pharmaceutical, Ltd., is a commercial model of the Scott Blair (1937) capillary-tube viscometer; a schematic diagram is shown in Fig. 1.A glass capillary tube T, 3 cm long, of 0067 cm internal diameter, which carries a male threaded boss, is screwed into a socket in the rheometer, and casts an image on a ground-glass screen S with a fiducial mark upon it. A synchronous motor M1 drives the screen, together with the lens by which the image is formed, at a constant rate of 1 cm/min along the axis ofthe horizontal capillary.Pressure is applied to one end of the capillary from a uniform rubber tube R of 1 cm diameter compressed between two rollers W which are rotated by a handle, in such a way as to maintain the image of the meniscus of the fluid in the capillary tube coincident with the fiducial mark on the screen. The rollers are connected by a variable gearbox G to a stylus P which records laterally upon a drum D the change in length of the rubber tube; and thus, since the changes in length of the tube are small and Boyle's law can be applied, the extrusion pressure in the capillary is also defined. The drum is rotated at a rate equivalent to a recording speed of 4 cm/min by a second
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