THE EFFECT OF VARIABLE PERSPECTIVES ON JUDGMENTS OF OPINION STATEMENTS FOR THURSTONE SCALES: EQUAL-APPEARING INTERVALS.

A closure cap which is applied to the closed neck of an infusion flask to provide a sterile seal therefor comprises a tear-off portion which when removed exposes a sealing disc which can be perforated by the canule of a syringe. The sealing disc is cast or moulded within the cap in engagement with the end wall of the cap and the tear-off portion therein, the said portion having at least one projection on its inner face which locally reduces the thickness of the sealing disc by providing an indentation in the disc which identifies a prepared point of perforation. The closure cap can be fixedly connected to the neck of the flask, and locating means may be provided on the cap and the flask to determine a preset rotational position of alignment of the cap and flask.