The varying of the parotid secretion with the nature of the food taken, is considered by M. Bernard to be a proof that this secretion is especially intended to favour mastication. A horse kept on perfectly dry food gives out a far greater quantity than when the food is moistened. Experiments on the dog and rabbit supplied similar results; and, extraordinary as it may appear, the gland will secrete saliva in the course of an hour weighing eight or ten times as much as its own tissue. A striking example this of the rapidity with which saliva can be separated from the blood under certain circumstances, and of the fallacy of founding conclusions on the quantity secreted within the twenty-four hours.
The sublingual gland is inert during mastication, and only begins to act as swallowing commences, when it envelops or lubricates the chewed substance with a fluid that assists its passage to the stomach. The function of the submaxillary has much to do with taste; the fluid which it pours out dilutes and diminishes the pungent flavour of sapid substances, and at the same time weakens the energy of their contact. The three organs are identical in texture, though so different in their secretions; 'each gland,' as M. Bernard says, 'having a special act, its function is exercised under separate and independent influences. Notwithstanding their discharging into and mixing in the mouth, their use remains distinct,' as above stated. To complete this brief summary of an interesting subject, it may be added, that birds and reptiles have but one kind of saliva, answering to the viscous in mammalia.
M. Vogt, in a communication to the Académie, adds to the proofs that what is called the spontaneous generation of certain worms, is due to natural causes. For instance, a worm, which has no reproductive organs, is often found in the body of the stickle-back; this worm, however, is known to breed, but it does so only when the stickle-back happens to be eaten by a bird; the worm is then placed in the proper condition for development, 'for it is then only that its segments become filled with eggs, which, egested by the bird, pass into the bodies of other fishes;' in a way more in accordance with natural operations than spontaneous generation.
Again, of two kinds of worms which infest human beings, the Bothriocephalus is found among the Poles, Swiss, and Dutch, while the Tenia, or tape-worm, is common among the French and Germans. If, however, the latter reside in Switzerland, they also become infested with the first-named worm, the reason given being, that in Switzerland liquid excretæ from cesspools are largely used for manuring vegetables, and that, in the eating of these vegetables, the eggs of the worms are taken into the body, and become hatched by means of the intestinal warmth. These investigations, which are to be continued, are important, seeing that they have a bearing on the phenomena of health and disease.
There are some curious facts, too, concerning oysters. M. Dureau de la Malle states, that 100,000,000 of these bivalves are collected annually from a bank off the port of Granville; and that, by a proper course of feeding, white oysters have been converted into a much esteemed green sort, which sell at a high price. And further, a physician at Morlaix has succeeded in crossing a big, tough species with one that is small and delicate, and has obtained 'hybrids of large size and of an excellent quality.'
M. Verdeil informs the Académie, that he has proved the chlorophyll, or resinous green colouring-matter of plants, to be 'a mixture of a perfectly colourless fat, capable of crystallising, and of a colouring principle which presents the greatest analogies with the red colouring principle of the blood, but which has never yet been obtained in a perfectly pure state.' He has isolated a quantity for experiment and examination by a chemical process, and has added another fact to the list of those which shew a relation between animal and vegetable functions. It has been known for some time, that certain functions of the liver are similar to those of certain plants.
M. Marcel de Serres shews, that marine petrifactions are not necessarily of ancient date, for they are formed at the present day in existing seas; that shells are now being petrified in the Mediterranean. All that is required for the result, is the presence of certain calcareous salts in the water; repose even is not essential, for the process goes on below, though the surface may be stormy. These petrifactions are not, as some suppose, to be regarded as fossils, the latter designation belonging only to 'those organic remains which are found in geological deposits.'
Apropos of the burning of the Amazon: M. Dujardin relates, that a fire broke out a short time since in a spinning-mill at Douai. It penetrated to the carding-room; destruction seemed inevitable, and the engines were sent for, when it was proposed to fill the blazing room with steam. A steam tube traversed the apartment; it was broken by a stroke with an axe, the steam rushed out, 'and in a few minutes the conflagration was extinguished as if by enchantment.'
Attempts are still being made towards aërial navigation. M. Prosper Meller, of Bordeaux, proposes to construct an aërial locomotive 200 mètres in length, 62 wide, and 60 high, the form to be cylindrical, with cone-shaped ends, as best adapted for speed. The outer case is to be varnished leather, which is to be filled with gas, and to contain five spherical balloons. A net, which covers the whole, is to support sixteen helices by ropes, eight on each side; and to these two galleries are to be attached, one for the machinery, the other for passengers. The affair looks well on paper; but there is little risk in saying, that the days of flying machines are not yet come, neither is the scheme for aërial railways—a series of cables stretched from one high building to another—to be regarded as any more promising.