Covering apparatus and method for film mounted serial tissue sections

A method for impregnating with a substance which when dry is optically clear and covering with an optically clear cover serially mounted histologic tissue sections mounted on an optically clear film strip to prepare the sections for viewing and where the sections are in the state, following embedding, of having been sliced to a thickness within the 3-12 micron range, of having been serially adhered to one side of said strip, of having been stained and of having had the embedding medium removed from the tissue interstices, comprising the steps:

• a. mounting on a film reel adapted for rotation a length of at least three feet of said film strip having serially mounted and adhered thereon a plurality of said 3-12 micron thick sections in said stained state;
• b. rotatably mounting proximate said film reel a convolutely wound roll of adhesive tape in continuous tape form, said tape consisting of an optically transparent backing strip and on one side of said strip a coating of pressure sensitive adhesive substance characterized by being dissolvable in a selected solvent, in a dissolved state being adapted to impregnate the interstices of said stained tissue sections when submerged therein and in a dry state when confined in said interstices being optically clear;
• c. pulling said tape and film from the respective roll and reel such that the side of said film mounting said sections and the side of said tape having said adhesive substance is guided to a station wherein said tape is maintained flat and horizontal during its travel and with said tape adhesive coated side disposed upwardly and at such said station said film is maintained flat and angled downwardly during its travel at an acute included angle with respect to the tape and with the mounted side of said film having the adhered serial sections disposed downwardly whereby to merge the entire surface of said tape adhesive coated side with the entire surface of said film mounted side and to thereafter bring the entire respective merged surfaces of the tape and film in a closely merged relation preparatory to being rolled into a coil;
• d. providing at said station immediately prior to the place of said merger a flow of said selected solvent in which said tape adhesive substance is soluble, said solvent including a predetermined quantity of an additional adhesive substance dissolved therein, said amount of additional adhesive substance being selected to provide at the place of merger a flow of sufficient solvent over the entire surface of said tape coated side to combine with the tape adhesive thereon to insure such tape adhesive being sufficiently dissolved in a selected period of minutes to fully impregnate the interstices of said stained sections and with sufficient additional and compatible adhesive substance being supplied to insure said interstices being filled during the completion of said merger and following such merger to leave said stained sections optically clear;
• e. taking up such merged film-tape in a convolutely wound roll at a predetermined speed and tension selected to allow said mixture of solvent and adhesive substance to cover said entire surface of said tape coated side prior to said merger and to allow said roll to be formed without damaging said sections;
• f. after said merger allowing the merged tape film to rest in a firmly wound convolute form for a predetermined period of minutes to complete the impregnation of said sections by said dissolved adhesive substances and the setting of such substances;
• g. after said period of minutes rewinding said merged tapefilm into a convolutely spaced reeled form for drying;
• and
• h. drying said merged tape-film while in said convolutely spaced relation to evaporate said solvent and complete the setting of said adhesive substances.