OCR Text |
Show of absorbing fluids: I suppose this last performed in the following way 1-The liquid to be absorbed affects the mouth ofthe absorbent, and determines it to give it admission or not. Ifit gives itadmission, the first part of the lym- phatic absorbs it, perhaps, as has been supposed, by its action, as a capillary tube, or from a livingpower. Conclusion (film First Part. Conclusion (y' tbs Firrt Part. This fluid having entered, and filled the firstpart of the absorbent, now stimulates its internal cavity, which again contracting, propels the fluid towards the. trunks of the system, as the valves do not permit it to relapse into the cavity from whence it was absorbed. Having propelled the fluid it last absorbed, the mouth of the vessel relaxes again, becomes empty, and a fresh quantity is taken in, as long as any fluid pre- sents itself. It is not certain that absorption of fluids does not begin, in the extremities of vessels, on the principle of capillary attraction only: this was the opinion of Aggiunti. But there is something in the action of the absorbing orifices which resembles selection; nor is the absorption so constant or uniform as capillary attraction tnust necessarily be. If the end or an empty capillary tube is immersed in a fluid, the fluid must rise in it, if it meets with no obstruction; but the extremities of the lacteals are often immersed in chyle without taking up any of it, as I saw in the orifi- 111 that ofa caterpillar eating up the leaf ofa tree; and believes that the absor- bents elongate themselves, or shorten themselves, as their object recedes or approaches nearer. He even believes that the absorbing vessels of surrounding living parts are capable of elongating themselves, and of ab- sorbing dead bone, which we see sometimes partially and sometimes wholly removed. "'e know that the lymphatics certainly take up solid particles; there can hardly be a doubt of their absorbing the powder of calomel from the surface of the body, and that they carry it into the blood-vessels. The globules ofquicksilver, in the best prepared mercurial ointment, are never so small but that they may be distinctly seen in the microscope; and yet we know that they are absorbed. It is possible that, previous to the absorption ofa solid, the parts imme- diately to be absorbed may be broke down, mixed with, oreven converted into fluids. It is the opinion ofsome, that there is one menstruum in the body, which is actually capable of converting a solid into a fluid, the gastricjuice,antl that it converts various solids into one constant and uniform fluid, the chyle. The arteries may secrete a fluid on the surfaces ofbones, on particular occa- sions, capable ofdoing the same thing; or there may be also a fermentation, pe- culiar to the solids ofa livingbodyunder certain circumstances, by which they ces of the lacteals on the intestines; for some of the villi we loaded with may be decomposed and converted into fluids, retaining all the elementary chyle, whilst others almost in contact with them were entirely empty. Boerhaave says, that the absorbed fluids rush into the lacteals and lympha- tics; because the thoracic duet, contracting on its contents, is constantly forming vacuums; and that the velocity with which air rushes into the ex- hausted receiver of an air-pump, is twicethat 0f the swiftest wind, or forty-four feet in a second, as he had proved. This I doubt, for no vacuum can be formed by emptiness in any part of the body, because the pressure of the atmosphere would always force the surfaces together, nnless perfectly defended by bone-If the absorption of fluids is diflicult to be explained, much more so is the absorption of solids. Mr. Hunter supposes that the absorbents take down solids by a kind of reverse action to that of the arteries in forming them. He does not pretend to know how this is actually performed ; but says, it is not more difficult to conceive absorants removing bone, than to conceive that the arteries form it, which they certainly do. He supposes they may have a power similar to that particles ofthe solids. Mr. Hunter allows a decomposing principle in the substance of teeth; and, speaking of their decay, arising from rottenness, says, " This is owing to the enamel loosing its regular and chrystalliscd " texture, and being reduced to a state of powder, from the attraction of " cohesion being destroyet." Fermentation has been observed chiefly in dead matter, and is commonly accompanied with ebullition and extrication of air; but fermentation may also take place, and I believe certainly does take place in living matter. Ebullition, or any evident motion, is not ne- cessary to constitute fermentation; after wine has undergone what is called its open fermentation, it continues, after it is bottled, to go through its secret fermentation, where no motion is evident, and, every body knows, requires time to ripen. All that is necessary in fermentation is, that the elementary particles be separated and recombined, so that the matter be converted into something different from what it was before. There are some facts .. «a_.=t:« m. tidy!" < 110 |