Table 2.

Rectilinear displacement of a cell moving through cyclindrical and helical tunnels

Type of tunnel	Track length, μm (column 1)	Total tunnel length, μm (column 2)	Rectilinear displacement of the cell, μm (column 3)	(column 4) column 2 minus column 3	Curvature of tunnels, column 4 divided by column 2
Cylindrical	322	322	222	100	0.31
Helical	2,156	277	241	36	0.13

Measurements were made on photographs of 20 tunnels of each type, generated during a period of 24 h. Calculation of curvature of tunnels shows that helical tunnels are straighter than cylindrical tunnels.