159 



and have seen them flow back, when they were not admitted, to seek other 

 easier entrances. 



I will not collect, in this place, superfluous arguments against the 

 theory of the Leyden professor, rejected at its birth by the physicians of 

 Montpellier, absolutely refuted, and now universally given up. Irritation 

 alone keeps the blood in the inflamed part ; for, when death, which puts 

 an end to all irritations, and relaxes all spasms : when I say, death comes 

 on, all slight inflammations are dissipated, and whenever they have not 

 been sufficiently intense, to induce transudation of the blood through the 

 parietes of the capillaries, into thecrco/a? of the organic tissues, the blood 

 flows back into the large vessels, and there is no trace of it left. It is thus, 

 that erysipelas of the skin disappears, that the pleura preserves its trans- 

 parency, in individuals affected, before death, with sharp pains in the 

 side. If to this, we add our ignorance on the real organization of the 

 nervous system, on the conditions absolutely required of the brain and 

 nerves, for the maintenance of life, we shall cease to be surprised, that the 

 opening of bodies has taught us no more on the real seat of disease, and 

 we shall confess with Morgagni, who, however employed, with great suc- 

 cess, this means of improving the art of healing, that there are number- 

 less diseases, of which, after death, no trace is left, and for the fatal ter- 

 mination of which, we are unable to account. 



Contractility and sensibility exist, in a much higher degree, in the ca- 

 pillary and serous vessels, than in the veins and arteries. Life must needs 

 be more active in the former, for, the motion given to the blood by the 

 contractions of the heart, being exhausted, this fluid, no longer in the 

 sphere of action of that organ, can circulate, viutfrom the influence of the 

 action of the vessels themselves. 



The termination of the arteries in veins, is the only well ascertained 

 termination of those vessels ; it may be seen by the help of the micro- 

 scope, in cold-blooded animals, in frogs and salamanders. In some fish, 

 \ve may, even with the naked eye, observe frequent and considerable 

 inosculations, between the arteries and veins. In man, however, and in 

 other warm-blooded animals, these communications take place, only 

 at the extremities of the two systems of vessels. In this case, the arte- 

 ries terminate, sometimes, in capillary vessels carrying serous fluid, such 

 as the vessels of the sclerotic coat; these vessels become small veins 

 whose calibre gradually increases, until they admit red globules in suf- 

 ficient number to reflect that colour. At other times, the artery and vein 

 are continuous, without the intervention of that extremely minute sub- 

 division: the red blood then passes readily and immediately from the ar- 

 tery into the vein*. 



It will be shown, in speaking of secretion, that the continuation of the 

 arteries into the excretory ducts of the conglomerate glands, and their 

 termination in exhaling orifices, cannot be admitted, and that the presence 

 of small pores, in the sides of the minute arteries and veins, would afford 

 an explanation of the phenomena on which the belief of this termination 

 of the arteries rests. There exists no parenchyma, no spongy tissue, be- 

 tween the extremities of the arteries and the origin of the veins, with, 

 perhaps, the exception of the substance of the cavernous bodies of the 



* See the Chapter on the Organs of Generation. 



