Bronc riding toward the rigging handle, spurring at each jump in rhythm with the motion of the horse. Bareback bronc riding began to develop as a professional rodeo sporting event around 1900. The riding equipment used during that era varied. In some cases, the rider simply held onto the horse's mane, called a mane-hold. Others held a loose or twisted rope tied around the horse's girth, and other methods involved using multiple handhold leather riggings based on a surcingle. In the early 1920s, when the old rodeo rules allowing two handed riding were being phased out and replaced with the newer rule
Animal testing on frogs which reaches its reproductive age in five months rather than one to two years (as in "X. laevis"), facilitating faster studies across generations. The genome sequence of "X. tropicalis" was scheduled to be completed by 2015 at the latest. Frogs are widely used in classroom dissections and teaching exercises. Animal testing on frogs Frogs have been used in animal tests throughout the history of biomedical science. Eighteenth-century biologist Luigi Galvani discovered the link between electricity and the nervous system through studying frogs. The African clawed frog or platanna, "Xenopus laevis", was first widely used in laboratories in pregnancy assays in