Abstract: A method for the manufacture of a hollow fiber membrane by mixing polypropylene, an organic filler capable of uniformly dispersing in the polypropylene in a fused state and easily dissolving in an extractant being used, and a crystal seed forming agent. The resulting mixture, in a molten state, is discharged in the shape of a hollow fiber through an annular spinning nozzle and into contact with a liquid made of said organic filler or a compound similar thereto. This results in cooling and solidifying the hollow fiber, which is then forwarded into contact with an extractant incapable of dissolving polypropylene, to remove the organic filler and form the membrane.

Abstract: Unstretched hollow fibers of cuprammonium cellulose for dialysis possessing a film structure having a porosity of 15 to 25%, a pore diameter of 25 to 40 .ANG., and an ultrafiltration ratio of 3.0 to 5.5 ml/mmHg.hr.m.sup.2 are obtained by extruding, coagulating, and regenerating a cuprammonium cellulose spinning dope having a cellulose concentration of 6.8 to 8.7% and a viscosity of 500 to 1,300 poises (at 20.degree. C.).

Abstract: This invention discloses a ventilating needle having a membrane-type filter stretched across the communication passage of a hub portion of the needle. In this invention, the membrane-type filter is of 2-ply type composed of a reinforcement layer and a water-repellent filter having a higher melting point than said reinforcement layer. This membrane-type filter is thermally adhered to a step portion formed in the inner wall of the hub portion through interfusion of the reinforcement layer and the step portion. This invention also discloses a method of assembling the ventilating needle in which a membrane-type filter is adhered to a step portion formed in the inner wall of the hub by means of ultrasonic waves.