It’s cold. My toes are numb again. Especially my left big toe. That seems to go first.

The big toes and the balls of my feet feel clumsy, insensate. In fact my feet feel like lumpy inert extensions of my legs.

The skin will be dead white.  Perhaps my toenail will fall.

In freezing temperatures the so-called glomus bodies constrict blood vessels close to the skin and shunt blood away from the extremities.

It took me a while to find out about glomus bodies.

The glomus bodies are tiny balls of tissue and muscle that divert the blood from one branch of the arterial system to another down small connecting arterioles.

You can see such tiny connections between the veins of a leaf.

It is called anastomosis and it comes from the Greek word for a cross-link between two branching streams.

Glomus bodies are controlled by the sympathetic nervous system.

The body is protecting itself from hypothermia, the cooling of the inner organs.

I also learned about other protective mechanisms like shivering. When you shiver the excitation of your muscles generates heat. I never realised that.

Or goose bumps — which make hair follicles stand on end. In hairy animals that helps to create an insulating layer and slows the movement of cold air across the skin.

I feel the windchill on my face.

I think of the horrors of frostbite when the water in the cells of the body starts to freeze.

I do my best to keep my chest and upper body warm and dry so the inner organs do not lose too much heat, so the warming blood can reach my hands and feet.

I am wearing a merino wool base layer, a gilet, a fleece and a cycle jacket. I have neoprene covers over my shoes.

Hawks are mewing and wheeling against a clear blue sky.

As I ride, hedges break the rays of the low winter sun into irregular flashes that confuse my vision.