to dissolve them, and to assimilate their juices to our nature.
"Do you say that the organic movements by which the brain exercises these functions are unknown? I reply that the action by which the nerves of the stomach determine the different operations which constitute digestion, and the manner in which they confer so active a solvent power upon the gastric juice, are equally hidden from our scrutiny. We see the food-materials fall into this viscus with their own proper qualities; we see them emerge with new qualities, and we infer that the stomach is really the author of this alteration. Similarly we see the impressions reaching the brain by the intermediation of the nerves; they then are isolated and without coherence. The viscus enters into action; it acts upon them, and soon it emits [renvoie] them metamorphosed into ideas, to which the language of physiognomy or gesture, or the signs of speech and writing, give an outward expression. We conclude, then, with an equal certitude, that the brain digests, as it were, the impressions; that it performs organically the secretion of thought." [Rapports du Physique et du Moral, 8th edition, 1844, p. 137.]
It is to the ambiguity of the word 'impression' that such an account owes whatever plausibility it may seem to have. More recent forms of the pro-
