Diastole

“ Briefly it was as follows: “The pulse consists of four parts, of a diastole and a systole, with two intervals of rest, one after the diastole before the systole, the other after the systole before the diastole.”504
His therapeutics were based on these two principles:—“1. That disease is something contrary to nature, and is to be overcome by that which is contrary to the disease itself; and 2. That nature is to be preserved by that which has relation with nature.”505
The affection contrary to nature must be overcome, and the strength of the body has to be preserved. ”

“ Whence the motion which is generally regarded as the diastole of the heart, is in truth its systole. And in like manner the intrinsic motion of the heart is not the diastole but the systole; neither is it in the diastole that the heart grows firm and tense, but in the systole, for then only, when tense, is it moved and made vigorous. ”

“ It is only truly distended, and in the proper state of diastole, when it is filled by the charge of blood projected into it by the contraction of the auricles; a fact which sufficiently appears in the course of vivisections. Descartes therefore does not perceive how much the relaxation and subsidence of the heart and arteries differ from their distension or diastole; and that the cause of the distension, relaxation, and constriction, is not one and the same; as contrary effects so must they rather acknowledge contrary causes; as different movements they must have different motors ”

“ But having judiciously and solidly explain'd the Systole, he contents himself to ascribe the Diastole to a motion of Restitution, which account gives me no Satisfaction: Because the Systole being the proper, and (as himself confesses) the only motion of the Heart, a State of Contraction seems to be the natural State, and consequently without External Violence, it shou'd have no Diastole at all. ”

“ When we see by the experiment just described, that the systole and diastole of the pulse can be accurately imitated without any escape of fluid, it is obvious that the same thing may take place in the arteries from the stroke of the heart, without the necessity for a circulation, but like Euripus, with a mere motion of the blood alternately backwards and forwards. ”

“ The movements of the heart consist of a series of contractions which succeed each other with a certain rhythm. The period of contraction is called the systole and that of relaxation the diastole. The two auricles contract and relax synchronously, and these movements are followed by the synchronous contraction and relaxation of the ventricles. Finally, there is a short period when the .whole heart is in diastole. ”

“ For I could neither rightly perceive at first when the systole and when the diastole took place, nor when and where dilatation and contraction occurred, by reason of the rapidity of the motion, which in many animals is accomplished in the twinkling of an eye, coming and going like a flash of lightning ”

“ Moreover, as each arterial diastole was due to an active expansion of the arterial wall, at each diastole there became blended with the contents of the arteries still more of the substance of the air, which was sucked into the arterial skin through the countless pores of the bodily skin, these being too fine to permit bleeding. The vital spirits, thus formed and modified, were blended with the blood of the arteries and supplied to the body at large. A part of these vital spirits mounted with the blood into the carotid arteries. ”

“ In moist and cowardly creatures, it is biggest.... Of all parts of the [233] body it is hottest, for it is the wellspring of life, and by arteries communicateth it to the rest of the body. The heart hath two motions, Diastole and Systole. In Diastole, or dilatation of the heart, the conus is drawn from the basis to draw blood by the cava to the right ventricle, and air by the arteria venosa [pulmonary vein] to the left ventricle. In Systole or contraction the conus is drawn to the basis.
“First, that the vital spirit may be thrust from the left ventricle of the heart into the aorta. ”

“ The diastole, I say, takes place from the blood swelling, as it were, in consequence of containing an inherent spirit, so that the opinion of Aristotle in regard to the pulsation of the heart,—namely, that it takes place by a kind of ebullition,—is not without some mixture of truth; for what we witness every day in milk heated over the fire, and in beer that is brisk with fermentation, comes into play in the pulse of the heart ”

“ The first distinctions of the pulse are derived from the extent of the diastole, according to its three dimensions, namely, length, breadth, and depth. These give rise to the characters long, broad, and deep or high. Le Clerc renders the last by élevé. A long pulse, of course, refers solely to the impression on the finger, as in reality one pulse cannot properly be said to be longer than another; but when a person is lean a larger portion of the artery can be felt under the finger than when he is fat. ”

“ The volume output per unit of time is greatly increased, the arch of the aorta is dilated, and the pulse is large. The fact that a large part of the blood regurgitates during diastole back into the ventricle, and the fact that the diastolic pressure is low means that there is no increased resistance to overcome, and the systolic pressure is not raised. ”

“ This condition may be recognised by the fact that contraction may be excited by mechanical and electrical stimuli or by the application of atropine solution; the latter paralyses the inhibitory nervous centres, and therefore sets the mechanism going again. The diastole of paralysis is the most frequent form of death. It may readily be distinguished from the muscarine diastole; for, in muscarine diastole, the heart is full of blood and larger than normal ”

“ A large volume of blood is thus at the disposal of the heart for it to draw on during diastole. Respiration by the aspirating action of the thorax sucks this blood into the heart, while the inspiratory descent of the diaphragm squeezes the abdominal contents and forces blood from the liver and cistern into the heart. These forces take the place of the sinus and are far more efficient. The intra-abdominal pressure may be raised on bending or straining till it becomes equivalent to the pressure of a column of mercury 80-IO0 mm. ”

“ When this condition has become perfected, compensation is established and the circulation is apparently normal. Nature causes these hearts, when they are disturbed or excited, to pulsate slowly, causing the diastole to be longer than in a heart with mitral regurgitation. This allows more blood to enter the left ventricle, and the left ventricle, acting perfectly on the blood which it receives, causes a good systolic pressure in the aorta and the systemic arteries. ”

“ The diastole of the heart is partly an active, partly a passive act. The cavities behave as would rubber balls, and their distension after contraction is partly due to their elasticity. The heart is a suction- as well as a force-pump. ”

“ Nokes in such terrible agonies, that any man would have swore he could not out-live another minute. I felt his pulse, and told him, that by the irregularities of his systole, and unequal vibration of his diastole, I knew as well what ail’d him,{136} as if I had seen him taken to pieces like a watch ”

“ For if in those fevers the arteries do not expand themselves in their diastole to more than half the usual diameter of their diastole in health, the fibres which constitute their coats, will move through a less space in a minute than in health, though they make two pulsations for one. ”

“ It is obviously of the utmost importance that the heart should not be over-dilated by an increased filling pressure during the period of diastole.
When a man strains to lift a heavy weight he closes the glottis, and by contracting the muscles which are attached to the thorax raises the intrathoracic pressure. The rise of intrathoracic pressure aids the pericardium in supporting the heart, and prevents over-dilatation by resisting the increase in venous blood pressure. This increase results from the powerful and sustained contraction of the abdominal and other skeletal muscles. ”

“ The prolonged diastole allows the ventricle time to completely fill, and the more forcible contraction causes the mitral valve to close more thoroughly and at the same time increases pressure in the coronary arteries, serving thereby the double purpose of relieving pulmonary engorgement and increasing heart nutrition. ”

“ But the movement of all cannot be equally well observed; for those which are situated in parts not fleshy may be more conveniently felt, whereas those that are in fleshy parts are more indistinct. Nor is any one more conveniently situated for being felt than the one at the wrist. The first kind of pulses is in regard to the time of their motion, as observed in systole and diastole. ”

“ Besides the arterial pulse already alluded to, produced by augmented intraocular tension, where the normal force of the circulation is not sufficient to drive the blood in a continuous stream into the tense eyeball, we have an analogous condition where the intraocular tension may be normal, but the arterial tension is diminished, and a full stream of blood can enter only during the diastole of the arteries or maximum of intravascular pressure. ”

“ The pulse pressure is subject to wide fluctuations but as a rule for any one normal heart it remains fairly constant as the rate varies. In a rapidly beating heart the diastole is short and the diastolic pressure rises. If the systolic pressure does not also rise, as in a normal heart following exercise, we will say, the pulse pressure falls. We know that when the pulse rate is constant, vasodilatation causes a fall in diastolic pressure and a rise in pulse pressure. On the contrary, vasoconstriction causes a rise in diastolic pressure and a fall in pulse pressure. ”

“ Whence it is affirmed, as by Hieronymus Fabricius of Aquapendente, in his book on “Respiration,” which has lately appeared, that as the pulsation of the heart and arteries does not suffice for the ventilation and refrigeration of the blood, therefore were the lungs fashioned to surround the heart. From this it appears, that whatever has hitherto been said upon the systole and diastole, on the motion of10 the heart and arteries, has been said with especial reference to the lungs. ”

“ Each pulsation consists of a sudden contractile movement downwards, corresponding to the systole of a beating heart, and a slower up movement of diastolic expansion. Application of [Pg 302] cathode at the pulvinule was found to exert a contractile reaction, exhibited either by the reduction of normal limit of diastolic expansion, or by an arrest of movement at systole. The effect of anode was precisely the opposite; the induced expansion was exhibited either by reduction of normal limit of systolic contraction, or by arrest of pulsation at diastole. ”

“ These facts, also, will afford abundant proof of what has already been said about the arteries; everywhere, in fact, such blood as is both specifically appropriate and at the same time thin in consistency answers more readily to their traction than does blood which is not so; this is why the arteries which, in their diastole, absorb vapour, pneuma, and thin blood attract either none at all or very little of the juices contained in the stomach and intestines. ”

“ Now let anyone make an experiment upon the arm of a man, either using such a fillet as is employed in bloodletting, or grasping the limb tightly with his hand; let a ligature be thrown about the extremity and drawn as tightly as can be borne. It will first be perceived that beyond the ligature the arteries do not pulsate, while above it the artery begins to rise higher at each diastole and to swell with a kind of tide as it strove to break through and overcome the obstacle to its current. ”

“ There is one remarkable experiment which I would have every one try who is anxious for truth, and by which it is clearly shown that the arterial pulse is owing to the impulse of the blood. Let a portion of the dried intestine of a dog or wolf, or any other animal, such as we see hung up in the druggists’ shops, be taken and filled with water, and then secured at both ends like a sausage: by tapping with the finger at one extremity, you will immediately feel a pulse and vibration in any other part to which you apply the fingers, as you do when you feel the pulse at the wrist. ”

“ The physician is required to note the patient's appearance, eye, tongue, skin, pulse, voice, urine, and faeces. The examination of the pulse is, however, considered the most important of all, as furnishing the best criterion of the phenomena and progress of disease, and it is the one usually depended upon by the native doctors. In order to know the precise character of the pulse, the radial artery at the wrist is usually chosen. In case of a male patient, his right pulse is generally felt, and in case of a female the left. ”