VANDERPUYE v. PIONEER SHOE FACTORY LTD. Negligence—Res ipsa loquitur—Application—Fire outbreak—Appellant alleging negligence against respondent—Failure of respondent to give evidence—Rebuttal evidence rather supplied by appellant's witness—Effect of absence of explanation by respondent—Res ipsa loquitur rule of evidence not substantive law—Previous cases of res ipsa loquitur not invariably and inflexibly binding precedents— Whether res ipsa loquitur applicable to fire cases.