Speaking of the second brain… A friend has brought it to my attention that D. H. Lawrence has written with tremendous relish on the subject of the second brain, or solar plexus:

In that little book, “Psychoanalysis and the Unconscious,” I tried rather wistfully to convince you, dear reader, that you had a solar plexus and a lumbar ganglion and a few other things. I don’t know why I took the trouble. If a fellow doesn’t believe he’s got a nose, the best way to convince him is gently to waft a little pepper into his nostrils. And there was I painting my own nose purple, and wistfully inviting you to look and believe. No more, though.

You’ve got first and foremost a solar plexus, dear reader; and the solar plexus is a great nerve center which lies behind your stomach. I can’t be accused of impropriety or untruth, because any book of science or medicine which deals with the nerve-system of the human body will show it to you quite plainly. So don’t wriggle or try to look spiritual. Because, willy-nilly, you’ve got a solar plexus, dear reader, among other things. I’m writing a good sound science book, which there’s no gainsaying.

Now, your solar plexus, most gentle of readers, is where you are you. It is your first and greatest and deepest center of consciousness. If you want to know _how_ conscious and _when_ conscious, I must refer you to that little book, “Psychoanalysis and the Unconscious.”

At your solar plexus you are primarily conscious: there, behind you stomach. There you have the profound and pristine conscious awareness that you are you. Don’t say you haven’t. I know you have. You might as well try to deny the nose on your face. There is your first and deepest seat of awareness. There you are triumphantly aware of your own individual existence in the universe. Absolutely there is the keep and central stronghold of your triumphantly-conscious self. There you _are_, and you know it. So stick out your tummy gaily, my dear, with a _Me voilà_. With a _Here I am!_ With an _Ecco mi!_ With a _Da bin ich!_ There you are, dearie.

(from read print)

And:

The primal consciousness in man is pre-mental, and has nothing to do with cognition. It is the same as in the animals. And this pre-mental consciousness remains as long as we live the powerful root and body of our consciousness. The mind is but the last flower, the _cul de sac_.

The first seat of our primal consciousnesses the solar plexus, the great
nerve-center situated behind the stomach. From this center we are first dynamically conscious. For the primal consciousness is always dynamic, and never, like mental consciousness, static. Thought, let us say what we will about its magic powers, is instrumental only, the soul’s finest instrument for the business of living. Thought is just a means to action and living. But life and action take rise actually at the great centers of dynamic consciousness.

The solar plexus, the greatest and most important center of our dynamic consciousness, is a sympathetic center. At this main center of your first-mind we know as we can never mentally know. Primarily we know, each man, each living creature knows, profoundly and satisfactorily and without question, that _I am I._ This root of all knowledge and being is established in the solar plexus; it is dynamic, pre-mental knowledge, such as cannot be transferred into thought. Do
not ask me to transfer the pre-mental dynamic knowledge into thought. It cannot be done. The knowledge that _I am I_ can never be thought: only known.

This being the very first term of our life-knowledge, a knowledge established physically and psychically the moment the two parent nuclei fused, at the moment of the conception, it remains integral as a piece of knowledge in every subsequent nucleus derived from this one original. But yet the original nucleus, formed from the two parent nuclei at our conception, remains always primal and central, and is always the original fount and home of the first and supreme knowledge that _I am I._ This original nucleus is embodied in the solar plexus.

(from online literature)

Terrific! Thanks very much, Alice.

See also this glorious diagram of the network of nerves in the abdomen, including the celiac plexus or solar plexus @ wikipedia).