But perhaps I had better leave your medical adviser to explain. After all, it is not necessary to go any further in this direction; the whole thing may be argued in terms of the blood stream--and the blood stream is respectable, as the duodenum is an outcast. It is the blood and the blood only, in fact, that the cerebrum is aware of; of what goes on elsewhere it can learn only by hearsay. If all is well below, then the blood that enters the brain through the internal carotid is full of the elements necessary to bestir the brain-cells to their highest activity; if, on the contrary, anabolism and katabolism are going on ineptly, if the blood is not getting the supplies that it needs and not getting rid of the wastes that burden it, then the brain-cells will be both starved and poisoned, and not all the king's horses and all the king's men can make them do their work with any show of ease and efficiency. In the first case the man whose psyche dwells in the cells will have a moment of inspiration--that is, he will find it a strangely simple and facile matter to write his poem, or iron out his syllogism, or make his bold modulation from F sharp minor to C major, or get his flesh-tone, or maybe only perfect his swindle. But in the second case he will be stumped and helpless. The more he tries, the more vividly he will be conscious of his impotence. Sweat will stand out in beads upon his brow, he will fish patiently for the elusive thought, he will try coaxing and subterfuge, he will retire to his ivory tower, he will tempt the invisible powers with black coffee, tea, alcohol and the alkaloids, he may even curse God and invite death--but he will not write his poem, or iron out his syllogism, or find his way into C major, or get his flesh-tone, or perfect his swindle.