Blood clot

“ Capillary loops grow into the coagulum, and migrated leucocytes from the adjacent blood vessels destroy the red corpuscles, and are in turn disposed of by the developing fibroblasts, which by their growth and proliferation fill up the gap with young connective tissue. It will be evident that this process only differs from healing by primary union in the _amount_ of blood-clot that is present. ”

“ It is found that clotting is especially accelerated whenever the blood touches a foreign tissue, for instance, the outer layers of a torn blood-vessel wall, muscle tissue, &c., i.e. in exactly those conditions in which rapid clotting becomes of the greatest importance. Yet another very pregnant fact in connexion with clotting is that if an animal be bled rapidly and the blood collected in successive samples it is found that those collected last clot most quickly. Hence the more excessive the haemorrhage in any case, the greater becomes the onset of the natural cure for the bleeding, viz. ”

“ Occasionally a distinct acceleration in the clotting, compared with the normal, may be observed. Wright has further ascertained in his excellent researches, that the clotting time can be influenced by drugs: calcium chloride, carbonic acid raise, citric acid, alcohol and increased respiration diminish the clotting power of the blood.
Recently Hayem has repeatedly called attention to a condition, that is probably closely connected with the coagulability of the blood. Although coagulation has set in, the separation of the serum from the clot occurs only very slightly or not at all. ”

“ In very slow clotting at a low temperature the white corpuscles appear in a layer on top of the clot, the buffy coat.
Of fibrin little is known, but its formation is the most important step in clotting, as its presence is absolutely essential. If it is removed by whipping, the blood will not clot. It is a delicate, stringy material, elastic and contractile, and contains certain salts of lime and magnesium, upon whose presence its power of coagulation depends. The coagulability of blood differs in different people and is occasionally so little as to make operation dangerous. ”

“ The last step in the change is the action of thrombin upon fibrinogen to form fibrin, and the clot is complete.
The intrinsic value to the animal of these changes is quite plain. The power of clotting and thus stopping haemorrhage is of essential importance, and yet this clotting must not occur within the living blood-vessels, or it would speedily result in death. That the tissues should be able to accelerate the process is of very obvious value. That the inner lining of the blood-vessels does not act as a foreign tissue is possibly due to the extreme smoothness of their surface. ”

“ The same is true of the blood of an ecchymosis whether there be a hematoma or only an infiltration between the tissues, or both. These clots represent more or less the form of the space occupied by the blood. In the case of the scalp a subcutaneous clot may be mistaken for a depressed fracture of the skull from the fact that the edges of the clot become very hard while the centre is still quite soft. A wound in which a large artery has been divided may present very little clotting in the wound if the opening is free and the blood has mostly escaped in a jet. ”

“ A maniac was restored to reason by the blood of a calf, and the most extravagant hopes were entertained. But many fatal accidents occurring, experiments upon human beings were forbidden by law, and transfusion soon fell into disuse. It has, however, been successfully practiced in several cases within the last few years, and is a method still in repute for saving lives.
COAGULATION.—When blood is exposed to the air, it coagulates. This is caused by the solidifying of the fibrin, which entangling the disks, forms the "clot." The remaining clear, yellow liquid is the serum. ”

“ Krahn nodded grimly. “I know you’re not lying,” he commented, “and so I’ll tell you a funny thing about that specimen— a fact which may go far to help solve the mystery of your uncle’s death. In that slide appear scraps of fibrin, platelets— the substances in blood which cause it to clot, you know— a terrific number of white blood corpuscles, which are the buzzards of the circulating stream, but almost no red blood corpuscles at all! Something seems to have attacked them— that something being the mysterious ‘poppy field’ you see. ”

“ Thrombosis—clotting in the vessel. Embolism, blocking of the vessel. Thrombus may form in any bloodvessel. Embolism occurs in arteries. Clot follows the blood current. Causes of clotting—fibrinogen, paraglobulin, fibrine ferment; foreign bodies; parasites; air; blood that has been exposed, transfusion; ærial germs; disease germs; chemical coagulants; high and low temperatures; breaches of endothelium; congestion or inflammation of the serosa; stasis of blood and extension of clot; ligature near a branch vessel: deoxidation and carbonization of blood, marasmus; neoplasms ”

“ The next day I was taken back to Leeds in a state of absolute helplessness, and, being got to bed in my own house, had to remain there for nine mortal weeks.
Some of the experiences of that time were curious. Phlebitis had set in, and for a time I was in serious danger from the formation of a clot of blood in one of the arteries. As is pretty generally known, whilst this state of things exists death may occur at any moment from the stoppage of the heart through the clot getting free and passing into the central organ. ”

“ The white corpuscles become entangled in the upper portion of clot, giving it a pale yellow look on the top, known as the buffy coat. As the clot is attached to the sides of the vessel, the shrinkage is more pronounced toward the center, and thus the surface of the clot is hollowed or cupped, as it is called. This remarkable process is known as coagulation, or the clotting of blood; and the liquid which separates from the clot is called serum. The serum is almost entirely free from corpuscles, these being entangled in the fibrin. ”

“ In any case of bleeding the patient may become weak or may faint, but unless the blood is flowing actively, this is not necessarily a serious sign, and the quiet condition of the circulation during the faint often assists nature in staying the bleeding, by allowing the blood to clot, and so block up any wound in a blood-vessel. ”

“ Into the wedge-shaped, elastic clot which now fills the wound from bottom to top like jelly in a mould, the leucocytes or white blood-cells promptly migrate and convert it into a mesh of living cells. They are merely the cavalry and skirmishers of the repair [Pg 41] brigade and are quickly followed by the heavy infantry of the line in the shape of cells born of the injured tissues on either side of the wound. ”

“ Once a clean clot is formed don’t destroy it. Never use the homely cobwebs to stop bleeding as they reek with germs of blood poison. The second important step is to exclude pus germs. They are fewer in the woods than in the city, but we must be exceedingly careful. ”

“ My name is Ryan White. I am sixteen years old. I have hemophilia, and I have AIDS.
When I was three days old, the doctors told my parents I was a severe hemophiliac, meaning my blood does not clot. ”

“ Thus the ratio of the globulin fraction to the albumin fraction may vary considerably, and again, one or other of the proteins may be quite specific for the animal from which it is derived.
Clotting.—If a sample of blood be withdrawn from an animal, within a short time it undergoes a series of changes and becomes converted into a stiff jelly. It is said to clot. If the process is watched it is seen to start first from the surfaces where it is in contact with any foreign body; thence it extends through the blood until the whole mass sets solid. ”

“ Thousands of heart attack victims are being saved by the rapid administration of drugs to dissolve blood clots. Soon, gene therapy may be able to prevent the smooth muscle cell multiplication that contributes to the narrowing of blood vessels. ”

“ Very constant also is a marked absolute, and often a relative, increase of eosinophiles and basophiles. Polymorphonuclear neutrophiles and lymphocytes are relatively decreased.
[p. 210] The red cells show the changes characteristic of a severe secondary anemia, except that nucleated reds are commonly abundant; in fact, no other disease gives so many. They are chiefly of the normoblastic type. Megaloblasts are uncommon. Blood-plaques are generally increased.
2. Lymphatic Leukemia.—This form may be either acute or chronic. There is marked loss of hemoglobin and red corpuscles. ”

“ Does not the restoration of the blood from its disorganized state, by means of bleeding, suggest an idea of a similar change being practicable in the solids, when they are disorganized by disease? And are we not led hereby to an animating view of the extent and power of medicine?
2. Blood of a scarlet colour, without any separation into crassamentum or serum, indicates a second degree of morbid action. It occurs likewise in the malignant state of fever. It is called improperly dense blood. It occurs in old people. ”

“ Myelocytes are rare.
The red corpuscles show the changes usual in severe secondary anemia. Erythroblasts are seldom abundant. Blood-plaques are decreased.
3. Pseudoleukemia (Hodgkin's disease) resembles lymphatic leukemia in that there is marked and progressive enlargement of the lymph-nodes. There is, however, no distinctive blood-picture. The changes in hemoglobin and red cells resemble those of a moderate symptomatic anemia, with rather low color-index. The leukocytes are commonly normal in number and relative proportions. ”

“ We may just mention that as a general rule he approves of bleeding after any accident. He disapproves of bleeding both at the onset and the crisis of a disease. In constitutions requiring bloodletting he holds that spring is the best season for it. Even in cases in which there is a deficiency of blood, but there is congestion in some particular part, he permits blood to be abstracted, in order to produce revulsion, the patient’s strength being recruited afterwards by a nourishing diet. ”

“ Lymphocytes are formed in the lymphoid tissues, including that of the bone-marrow. They constitute, normally, 20 to 30 per cent. of all leukocytes, or about 1000 to 3000 per c.mm. of blood. They are more abundant in the blood of children.
The percentage of lymphocytes is usually moderately increased in those conditions which give leukopenia, especially typhoid fever, chlorosis, pernicious anemia, and many debilitated conditions. A marked increase, accompanied by an increase in the total leukocyte count, is seen in pertussis and lymphatic leukemia. ”

“ Still, if an abnormal murmur, harsh or soft in character, become suddenly developed over the pulmonary or aortic orifice, where it was known not to have previously existed, it is a physical sign which points with much certainty to the presence of a heart-clot. Whenever the signs and symptoms given above which show disturbance in the heart's action occur in a similar sudden manner in the course of an inflammatory or cachectic disease, such as pneumonia, cancer, or phthisis, we should properly suspect the formation of an autochthonous or embolic clot in the heart. ”

“ The lymph deposited will be found lying in unorganized flakes, wanting its usual adhesive properties, and very slightly attached to parts, presenting little or no increased vascularity. The rapid manner in which these depositions take place, shows that they are separated from the blood without undergoing any very elaborate process. In this condition of the system, any organ upon which the disease falls, may rapidly become disorganized, or may readily mortify; and, after death, a tendency to rapid decomposition will be manifested. ”

“ When this can be done with a lancet, it is to be preferred to any other method; but where a vein cannot be found, recourse must be had to leeches or cupping.
The quantity of blood to be let must always be regulated by the strength, age, constitution, manner of life, and other circumstances relating to the patient. It would be ridiculous to suppose that a child could bear to lose as much blood as a grown person, or that a delicate lady should be bled to the same extent as a robust man. ”

“ Little impression can be made on an acute disease by the slow removal of even a large quantity of blood, as the organs have time to accommodate themselves to the loss, which might, for any good it will do, as well be dispensed with. Either bleed rapidly or not at all. The nearer the commencement of an ailment, in which you employ bleeding, the operation is resorted to, the greater the chance of its doing good; no time ought, therefore, to be lost in using the lancet, when once it is known to be required. ”

“ The blood is collected in a glass or plastic graduated container and stored under refrigeration. The study of blood donors has, incidentally, given insights into the physiology of bloodletting since the volume customarily removed from a donor is about the same in volume as that taken by a bleeder (one pint or 500 cc) . [86]
The annual physical examination today includes taking a small amount of blood from the finger or a vein in the elbow. This blood is then analyzed for the presence of biochemical components of such diseases as diabetes, anemia, arteriosclerosis, etc. ”

“ The affected glands actually contain the germs which have made their way to them through lymph channels under the skin. When the glands begin to swell, the critical period of limitation of the disease to the starting-point will soon be over and the last chances for a quick cure will soon be gone. At any moment they may gain entrance to the blood stream in large numbers. While the swelling of these glands occurs in other conditions, there are peculiarities about their enlargement which the physician looking for signs of the disease may recognize. ”