1672-6; LH 037, 02. 123v.
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The true opinion of Descartes appears to have been that animals think. Also in the book on the Method of contraries he appears to say this, indeed so that he should be more satisfying to the theologians, whose judgment he feared. In his final letter to Henry More he did not show himself to be in doubt, but in the book on the passions, which is among the last, he said of the brutes that perhaps they do indeed think. This Malebranche did not notice. Lord Tschirnhaus believed himself to be able to show that there are no animals that do not arise from other animals. Fleas and lice of various sorts are produced in various animals; various animals are able to produce themselves, where no animals were before. Redi performed experiments, [and] if he had followed them through, he would have arrived at this. There are at length certain black spots in men’s nostrils, and if they are pressed a sort of worm can be squeezed out of them, a larva, and this is confirmed by the example of pediculosis, but these perhaps demonstrate as much. Visible animals often arise from invisible ones that make the air full, from indetectible spiders [come] these webs that fly through the air, which are called vulgarly Mariengarn ['Mary's thread']. Fevers from the matter that has passed from the veins into the tissue. Of course the supply of nutriment brings about extravasation, as other causes do constantly. From here, blood is either expelled, or it stagnates. If this arrives at the heart, and there brings about a fright because of its unaccustomed nature, the consumed matter returns in due time, and from here arise intermittent fevers. Artificial fever, if you poke yourself with a needle in the thumb, where on account of the hardness of the skin matter is not expelled well, and thus is carried by the blood to the heart, and brings about a little fever. (Thus the doubt, for what is outside the vessels does not return to the heart.) In dysentery there arises from a certain irritating matter a motion that is contrary to the peristaltic motion of the intestines, and from here, if nature should become accustomed [to this], the man dies. Nor indeed can the one motion be made to harmonize with the other, and an untimely expulsion follows, and one that is opposed to nutrition. A simple cure, if a man should not depart from his chair, and if he is turned every two hours, remaining until something is expelled. Thereagter, a little concealed, he will sweat, and finally he will accept a hot broth. These [things] suffice[:] the elements expel the irritant, opium diminishes the irritation. You will cure fever without a febrifuge if you sweat thoroughly, bringing down the fever; a certain person (though unfortunately) sweat only a little prior to paroxysm. By a violent paroxysm the fright ceases, [and] the sweating ceases, and a slight cold is felt. Thereupon, in turn, heat and sweat [followed], and thus the fever ceased. (Fevers arising from wounds are artificial.) It is noteworthy how tuberculosis comes about.
