" In Governor General in Council vs Province of Madras(1) the Judicial Committee of the Privy Council observed : "For in a Federal Constitution, in which there is a division of legislative powers between Central and Provincial legislatures, it appears to be inevitable that controversy should arise whether one or other legislature is not exceeding its own, and encroaching on the other 's constitutional legislative power, and in such a controversy it is a principle, which their Lordships do not hesitate to apply in the present case, that it is not the name of the tax but its real nature, its "pith and substance" as it has sometimes been said, which must determine into what category it falls." In Prafulla Kumar Mukherjee and Others vs Bank of Commerce, Limited, Khulna(2) the Judicial Committee of the Privy Council quoted with approval the observations of Sir Maurice Gwyer C.J. in Subrahmanyan Chettiar 's case (supra) to the effect : "It must inevitably happen from time to time that legislation, though purporting to deal with a subject in one list, touches also on a subject in another list, and the different provisions of the enactment may be so closely intertwined that blind observance to a strictly verbal interpretation would result in a large number of statutes being declared invalid because the legislature enacting them may appear to have legislated in a forbidden sphere.