Introduction to Part II
We next develop the theme of bounding introduced in the opening passages of Part I. To help fix ideas, the reader might glance at the figure accompanying exercise (12.11) p. 69. Neither curve δ nor γ 1 is deformable to a point on this surface. However δ disconnects the surface, while γ 1 does not. Note also, that the three curves, γ 1, γ 2, γ 3, may be regarded as the complete boundary of a piece of the surface.