OCR Text |
Show 14 INTRODUCTION· When condensed this substance forms those laminre called membranes; the m:muranes, rolled into cylinders, form those more or less ramified tubes named vessels; th~ filaments called fibres are resolved into it, and bones are nothmg b~t the same thing indurated by the accumulation of ear~hy particles. The cellular substance consists of a combmatwn well known as gelatine, characterised by its _solu~ility in boiling water, and forming, when cold, a trembling Jelly· We have not yet been able to reduce the ~edullary m_atter to its organic molecules; to the naked _eye, It appears hke ~ sort of soft bouillie, consisting of excessiVely small globules; It is not susceptible of any apparent motion, but in it _resides _the admirable power of transmitting to the ME the ImpressiOns of the external senses and conveying to the muscles the orders of the will. It consti't utes the greater portion of the brai. n an d the spinal marrow, and the ne~ves which are ~ist:ibu~ed to a!l the sentient organs are, essentially, mere fasciculi of Its rami· fications. The fleshy or muscular fibre is a peculiar sort of filame~t, whose distinctive property, during life, is that of contractmg when touched or struck, or when it experiences the action of the will through the medium of the nerve. The muscles, direct organs of voluntary motion, are mere bundles of fleshy fibres. All vessels and membranes which have any kind of compression to execute are armed with these fibres. They are always intimately connected with nervous threads, but those which belong to the purely vegetative functions contract, without the knowledge of the ME, so that, al· though the will is truly a means of causing the fibres to act, it is neither general nor unique. The fleshy fibre has for its base a particular substance called fibrine, which is insoluble in boiling water, and which seems naturally to assume this filamentous disposition. The nutritive fluid or the blood, suqh as we find it in vessels of the circulation, is not only mostly resolvable into the general elements of the animal body, carbon, hydrogen, oxygen and azote, but it also contains fibrine and gelatine, almost prepared to contract and to assume the forms of membranes INTRODUCTION. 15 or filaments peculiar to them, all that is ever wanted for t~eir manifestation being a little repose. The blood also contams an.other combination, which is found in many animal fluids and sohds, call~d ~lburn_e~, whose characteristic property is that ~f coagulatmg m b01hng water. Besides these, the blood contams almost every element which may enter into th · · f e com-position o the. body of each animal, such as the lime and phosphorus .whic~ ha_rden the bones of vertebrated animals, the zron from whiCh It and various other parts receive their colour, the fat or animal oil which is deposited in the cellula su?stance to supple it, &c. All the fluids and solids of th~ ammal bod~ a~e composed of chemical elements found in the blood, and It IS only by possessing a few elements more or less! that eac? of them is distinguished; whence it is plain, that their formatiOn entirely depends on the subtraction of the whole or part of one or more elements of the blood, and in some few cases, on the addition of some element from elsewhere. !hese operations, by which the blood nourishes the fluid or sohd matter of all parts of the body, may assume the general name ~f secretions. This name, however, is often appropriated e~cl~sively to the production of liquids; while that of nutritzon Is more especially applied to the formation and deposition of :he matter necessary to the growth and conservation of the sohds. . The compositio~ of every solid organ, of every fluid is pre~ Isely such as fits It for the part it is to play, and it preserves It as l?ng as health remains, because the blood renews it as !ast a~ It ?ec~mes changed. The blood itself by this continued ont_nbutw~ lS changed every moment, but is restored by di? estion, WhiCh renews its matter by respiration, which delivers It f:om superfluous carbon and hydrogen, by perspiration and d varwus _ot~er excretions, that relieve it from other superabunant prmc1ples. These perpetual changes of chemical composition form a part of the vital vortex, not less essential than the visible ~o~ements and those of translation. The object of the latter s, 111 fact, but to produce the former. |