The blood clotting system or coagulation pathway, like the complement system, is a proteolytic cascade. Each enzyme of the pathway is present in the plasma as a zymogen (inactive form), which on activation undergoes proteolytic cleavage to release the active factor from the precursor molecule. The coagulation pathway functions as a series of positive and negative feedback loops which control the activation process.
Spring Yard Zone is the third Zone in the original Sonic the Hedgehog. It is an urban level with many springs and bumpers, resembling a pinball machine. There are many secret areas in this zone. Act 2 has two Robotnik signs (goals) and as such, can be ended through two possible routes.
In 1959 the international yard and pound agreement (between the United States and countries of the Commonwealth of Nations) defined a yard as being exactly 0.9144 metres, which in turn defined the foot as being exactly 0.3048 metres (304.8 mm).