Axons cross from one side of the spinal cord to the other through the

Axons

Explanation:

Axons cross from one side of the spinal cord to the other through the gray commisure

Each arm or extension of the gray matter in the spinal cord is referred to as a hornProjecting towards the back of the spinal cord are the dorsal horns (or posterior horns)Projecting towards the front are the ventral horns (or anterior horns) In the thoracic and upper lumbar regions of the cord, an additional pair of side projections occur, which are called the lateral hornsA narrow band of gray matter known as the gray commissure stretches across of the center of the spinal cord and connects the two sets of hornsIn the middle of the gray commissure is the central canal, which contains cerebral spinal fluid

Gravitational force i believe

There would be no evaporation so no water cycle