1 Crossed Modules and Cat1-Groups 4 1.1 Pre-crossed and Crossed Modules . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 1.2 Examples of Crossed Modules . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 1.3 Properties of Crossed Modules . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 1.4 Sub-crossed modules . . . . . . . . . . . . . . . . . . . . . ....

All paired muscle systems are represented in the brain by paired controlling centres. Dominance, or leading control of the function, may be entirely leftsided, in which case the organs controlled are dominant on the right side, or entirely right-sided. If some centres are on the left and some on the right side of the brain, the condition is called crossed laterality. The dominance may be fixed,...