They disappeared by the striae being replaced by transverse lines formed of excessively minute dark points, which towards the exterior could be seen only under a very high power; and ultimately these points were lost. When I made these observations, I had not read Schiff's account* of the digestion of meat by gastric juice, and I did not understand the meaning of the dark points. But this is explained in the following statement, and we further see how closely similar is the process of digestion by gastric juice and by the secretion of Drosera.

["On a dit le suc gastrique faisait perdre la fibre musculaire ses stries transversales. Ainsi nonce, cette proposition pourrait donner lieu une quivoque, car ce qui se perd, ce n'est que l'aspect extrieur de la striature et non les lments anatomiques qui la composent. On sait que les stries qui donnent un aspect si caractristique la fibre musculaire, sont le rsultat de la juxtaposition et du paralllisme des corpuscules lmentaires, placs, distances gales, dans l'intrieur des fibrilles contigus. Or, ds que le tissu connectif qui relie entre elles les fibrilles lmentaires vient se gonfler et se dissoudre, et que les fibrilles elles-mmes se dissocient, ce paralllisme est dtruit et avec lui l'aspect, le phnomne optique des stries. Si, aprs la dsagrgation des fibres, on examine au microscope les fibrilles lmentaires, on distingue encore trs-nettement leur intrieur les corpuscules, et on continue les voir, de plus en plus ples, jusqu'au moment o les fibrilles elles-mmes se liqufient et disparaissent dans le suc gastrique. Ce qui constitue la striature, proprement parler, n'est donc pas dtruit, avant la liqufaction de la fibre charnue elle-mme."]

In the viscid fluid surrounding the central sphere of undigested meat there were globules of fat and little bits of fibro-elastic tissue; neither of which were in

* 'Leons phys. de la Digestion,' tom. ii. p. 145. [page 100]

the least digested. There were also little free parallelograms of yellowish, highly translucent matter. Schiff, in speaking of the digestion of meat by gastric juice, alludes to such parallelograms, and says:--

["Le gonflement par lequel commence la digestion de la viande, rsulte de l'action du suc gastrique acide sur le tissu connectif qui se dissout d'abord, et qui, par sa liqufaction, dsagrge les fibrilles. Celles-ci se dissolvent ensuite en grande partie, mais, avant de passer l'tat liquide, elles tendent se briser en petits fragments transversaux. Les 'sarcous elements' de Bowman, qui ne sont autre chose que les produits de cette division transversale des fibrilles lmentaires, peuvent tre prpars et isols l'aide du suc gastrique, pourvu qu'on n'attend pas jusqu' la liqufaction complte du muscle."]

After an interval of 72 hrs., from the time when the five cubes were placed on the leaves, I opened the four remaining ones. On two nothing could be seen but little masses of transparent viscid fluid; but when these were examined under a high power, fat-globules, bits of fibro-elastic tissue, and some few parallelograms of sarcous matter, could be distinguished, but not a vestige of transverse striae. On the other two leaves there were minute spheres of only partially digested meat in the centre of much transparent fluid.

Fibrin.--Bits of fibrin were left in water during four days, whilst the following experiments were tried, but they were not in the least acted on. The fibrin which I first used was not pure, and included dark particles: it had either not been well prepared or had subsequently undergone some change. Thin portions, about 1/10 of an inch square, were placed on several leaves, and though the fibrin was soon liquefied, the whole was never dissolved. Smaller particles were then placed on four leaves, and minute [page 101] drops of hydrochloric acid (one part to 437 of water) were added; this seemed to hasten the process of digestion, for on one leaf all was liquified and absorbed after 20 hrs.; but on the three other leaves some undissolved residue was left after 48 hrs.

Charles Darwin

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