Volume 1

A text-book of human physiology : including histology and microscopical anatomy with special reference to the requirements of practical medicine / by L. Landois ; translated from the seventh German edition with additions by William Stirling.

Landois, L. (Leonard), 1837-1902. Lehrbuch der Physiologie des Menschen. English

Date:: 1891

Credit: A text-book of human physiology : including histology and microscopical anatomy with special reference to the requirements of practical medicine / by L. Landois ; translated from the seventh German edition with additions by William Stirling. Source: Wellcome Collection.

152/602 page 112

$J12 DIVISION AND LIGATURE OF BLOOD-VESSELS. [SeC. 65. cases where no structural changes can be found]. Marasmus preceding death causes the arteries to become wider than normal. In some old people they become atheromatous and even iThf capillaries by the thinness and permeability of their walls are well adapted for the exchange between the fluids and gases of the blood which they contain, and the tissues lying outside themT while by their extensibility and elasticity they can adapt their calibre to the nrpqqnrp and a'uantitv of blood within them.] . . -j. .-u ^ Uses of Elasticity.-The elasticity of the arteries is of the utmost importance m aiding the conversion of the unequal movement of the blood in the large arteries into a uniform flow in the P^Krie^ E H. Weber compared the elastic wall of the arteries with the air in the air- chCber of a fi're-engine. In both cases an elastic medium is acted upon-the air ni the one äse and the elastic tissue in the other-which in turn presses upon the fluid, propellmg t onwards continually, while the action of the pump or the heart, as the case may be, is mter- nSnt The ordinary spray-producer acts on this principle. A uniform spray or jet is obtained by pLpingi/^^^ but only when the resistance is such as to bring into action the elasticity of the bag between the pump and the spray-orifice.] Cohesion—The cohesion of blood-vessels is very great, and in virtue of this thev are able to resist even considerable internal pressure without giving way. ihe carotid of a sheep is ruptured only when fourteen times the usual pressure it is called upon to bear is put upon it (Volkmann), Given a vein and an artery 0/ the sa^ne thickness, a greater pressure is required to rupture the former than the latter. The huitTcarotid or iliac artery resists a pressure of 8 atmospheres, the veins about '^'rSon of anArte an artery is divided in the living body, the blood spouts in jets from the proximal cut end of the tube, the heart end. Each iet forms a parabolic curve, and the flow does no cease between the jets • If a large artery be severed, the blood may be projected for a distance of several feet this being greater the larger the artery and the nearer it is to the heart. A very small aniSunt of blood may flow from the distal cut end. This will depend on the extent to which collateral anastomosis takes ]3 ace.J ^ , , , [In the case of a divided vein, the blood flows chiefly from the distal end, and it does not come in jets, but as a slow continuous flow. The flow from the centra end may be almost n/Z or very slight, but this again depends on the amount of Kluttf t'i^^^^ ruptures the inner coat, and the vessel swells on the nroximal side of the ligature, while immediately after the ligature is applied the distal part of the vessel, i.e., the part beyond the ligature, collapses and becomes SÄ and no pulse is felt in it, while the pulse is felt m the proximal part right ^LiiuÄ the vein to swell on the distal side of the ligature, whüe on the proximal or cardiac side it collapses, unless there be a very free 7onaW circulation. No pulse is felt on either side of the ligature. These results necess^^^^^^^^^^ from the course of the blood-stream-movmg as it does m opposite directions—in the two vessels.] 66. INVESTIGATION OF THE PULSE.—[The characters of the pulse may be investigated by— , . /. ^ • \ ^ (1) The eye (inspection). (2) The flnger (palpation). (3) Instruments. The examination is usually confined to that part of the radial artery which . lies immediately above the wrist, with the flexor tendons internal to it, and the rid<.eTthe racUus on its outer aspect, while the shaft of the radius forms a firm W support against which the artery can be compressed by means of the finger. WhenTfinger is placed on the radial artery-covered here only by skm and sub- cutaneous tissue-or on any artery in the living body, one feels a distinct sense of$