Circulation of blood

“ This circulation is maintained by means of a pumping organ or heart, which receives the blood from the veins and by the contraction of its powerful walls forces this into the arteries, the direction of flow being determined as in a pump, by a system of valves. The waste products of cell life pass from the cells into the fluid about them, and are in part directly returned into the blood, but for the greater part pass into it indirectly through another set of vessels, the lymphatics. ”

“ But it is necessary that the heart shall be assisted considerably, in the circulation 357 of the blood, by a contractile power of the vessels themselves; and the same quantity of blood is not to circulate in the same body at all times, for animals are liable to frequent injuries, by which the quantities of blood in their bodies may be very suddenly reduced. ”

“ It will be always a difficult thing to prove, that the secretions, the exhalations, and the process of nutrition, could not be made from venous blood, because the circulation of this sort of blood in the arteries, does not continue for a sufficient time, to allow of observations, or the manner in which these functions would be affected by it. ”

“ But I trust that we have facts enough to establish it as a certainty, 1st, That the black blood after the interruption of the chemical functions of the lungs, continues for some time to circulate, and 2dly, That it penetrates into the organs, where it replaces the red blood; these circumstances explain the reason, why on opening the body we always meet with black blood even in the vessels which are destined for the circulation of arterial blood. ”

“ It is in this sense that the heart, so remarkable for its cavities, should be reckoned a workshop, source, perpetual fire-place; it is like a hot kettle by virtue, not of its body, but of its contained blood, in the same sense in which the liver, the spleen, the lungs, and other parts are reckoned hot; because they contain many veins or vessels containing blood. In this way also I maintain that the native heat, or innate warmth, being the common instrument of all the functions, is likewise the prime efficient cause of the pulse. ”

“ In the blood, while it is circulating briskly in its vessels, there are distributed through it, without contact with each other, the millions of oxygen carriers called blood corpuscles. In the circulation in the free channels of the body, the arteries and veins, it is motion that keeps these corpuscles apart; we draw a drop of blood and let it come to rest on the microscope glass, and as the motion ceases the separated corpuscles run together, and adhere so firmly that we cannot easily separate them without their disintegration. ”

“ For the present be it enough to have shown sufficiently that during the beat of the heart the blood is transfused and withdrawn from the veins into the arteries through the ventricles of the heart, and is distributed to the body at large. ”

“ Pulsation, therefore, is accomplished by a double agency: that is to say, the expansion or dilatation is accomplished by the blood, but the contraction or systole is accomplished in the egg by the membrane of the vesicle, in the fœtus after birth by the auricles and ventricles of the heart; and these alternate and mutually associated efforts once begun, the blood is impelled through the whole body, and thus the life of animals is perpetuated. ”

“ The only way in which an increased blood supply can be obtained is by causing the blood to flow more rapidly. This is precisely what happens every time the blood pressure in the body rises. Whenever the vasoconstrictor center sends nervous discharges into the blood vessels of the skin and abdominal organs, causing them to contract, there is a diversion of blood from them directly into the skeletal muscles and also a rise in blood pressure due to the increase in resistance to the circulation, which causes blood to flow more rapidly through the brain. ”

“ After injury the dilatation of the vessels with the greater afflux of blood to the part is the effect of the greatly increased cell activity, and is a necessity for this. In many forms of disease it has been found that by increasing the blood flow to a part and producing an active circulation in it, that recovery more readily takes place and many of the procedures which have been found useful in inflammation, such as hot applications, act by increasing the blood flow. ”

“ But such experiments are not applicable to the blood. Though that of the arteries may be somewhat hotter than the venous blood, yet the reason is obvious. The heat is communicated directly to the arterial blood in the lungs; but during the circulation a part of it evaporates, and the farther distant any part is from the lungs, the more cool will the vital fluid be, without regard to any alteration of capacity, which indeed never can be shown to exist. ”

“ This experiment will contradict those who pretend that the blood in the arteries is of one kind, that in the veins of another, on the ground that that in the arteries is more florid and seethes and is blown up with copious spirits, I know not how, like milk or honey boiling upon the fire, swelling and filling a larger space. ”

“ But this deficiency of arterial blood may be depending on a more positive cause, venous congestion, impeding its flow; for in sleep, the breathing being slower, the blood becomes essentially darker. Even arterial blood itself will become to a certain degree carbonized, by lentor, or stagnation. Venous congestion and diminution of arterial circulation are not incompatible ”

“ In the sanguine temperament all the vital functions are more active, the blood itself has a deeper hue, its corpuscles carry more oxygen, the complexion is quite florid, and the arterial currents impart to every faculty a more hopeful vigor. The blood-vessels are the most active absorbents, eagerly appropriating nutritive materials for the general circulation, while the respiration adds to it oxygen, that agent which makes vital manifestation possible. ”

“ Among the researches of the last thirty years, those bearing on the Circulation of the Blood must take an important place, both for their physiological interest and for the weighty influence they have exerted on our knowledge and treatment of disorders of the vascular system, such as heart disease. ”

“ For this purpose, if the pulse is full and frequent, some blood may be taken from the arm, and the patient should be kept in the horizontal position, surrounded by cool air, cold applications made over the hypogastrium, and acetate of lead and opium, mineral acids, and other remedies that diminish the force of the circulation and promote the coagulation of the blood, should be taken internally. The plug is here totally inadmissible; it can only convert an external into an internal hemorrhage. ”

“ But indeed, supposing even the smallest quantity of blood to be passed through the heart and the lungs with each pulsation, a vastly greater amount would still be thrown into the arteries and whole body, than could by any possibility be supplied by the food consumed ”

“ There is no pulse, because there is no blood in the arteries." "There are also lethargy and languor, and oppression in breathing, caused by the blood being collected in the veins. These make up the principal links in the chain of mechanical symptoms." ”

“ As the lungs alone receive the whole blood of the body, when their forces are weakened, the blood stagnates and accumulates in them; so that according to the state of their forces in the last moments, and the disease, these organs will be more or less heavy, and more or less full of blood. ”

“ Some, whilst they attempt to lessen the difficulty here, affirming that the blood is spirituous and arterious, virtually concede that the office of the arteries is to carry blood from the heart into the whole of the body, and that they are therefore filled with blood; for spirituous blood is not the less blood on that account. ”