37. When, from a cause which preceded the imposition of an easement, the person by whom it was imposed ceases to have any right in the servient heritage, the easement is extinguished. Exception.-Nothing in this section applies to an easement lawfully imposed by a mortgagor in accordance with section 10. Illustrations (a) A transfers Ulipur to B on condition that he does not marry C. B imposes an easement on Ulipur. Then B marries C. B's interest in Ulipur ends, and with it the easement is extinguished. (b) A, in 1860, let Ulipur to B for thirty years from the date of the lease. B, in 1861, imposes an easement on the land in favour of C, who enjoys the easement peaceably and openly as an easement without interruption for twenty-nine years. B's interest in Ulipur then ends, and with it C's easement. (c) A and B, tenants of C, have permanent transferable interests in their respective holdings. A imposes on his holding an easement to draw water from a tank for the purpose of irrigating B's land. B enjoys the easement for twenty years. Then A's rent falls into arrear and his interest is sold. B's easement is extinguished. (d) A mortgages Ulipur to B, and lawfully imposes an easement on the land in favour of C in accordance with the provisions of section 10. The land is sold to D in satisfaction of the mortgage-debt. The easement is not thereby extinguished.