When the emboli possess irritating or poisonous qualities, such as those derived from the puriform softening of venous thrombi in cases of septic inflammation, the mechanical effects will be the same as those previously described. These emboli, however, set up a suppurative in flammation in their vicinity, wholly inde pendent of any circulatory obstruction, and giving rise to pyremic abscesses in all parts of the body, while the effects of obstructed circulation are more or less local in character. Simple emboli small enough to become first arrested in the capillaries either produce no permanent change, or, at most, a punctiform haem orrhage; infectious emboli, however, oc casion the miliary abscesses observed in pyremia.
—If the occluded artery be of some size and supply important organs, the symptoms will be those of temporary arrest of function of the part supplied by the artery, as transient paralysis, dysp Inca, coldness of the extremities, etc. Should the artery be small, and not sup ply important organs, no symptoms may be caused.
Fat-embolism. — Fat-embolism is caused by injuries, especially those of the bones and soft parts in which there is an abundance of fat, especially when there is considerable crushing of the parts and many fat-cells are broken down and lib erated. These minute fat-globules min gled with the effused fluids and wound secretions may enter the circulation through the lacerated vessels and produce positive symptoms, the severity of which depend upon the quantity of fat which has gained entrance into the circulation and the rapidity with which it has en tered.
— The symptoms usually develop within from thirty-six to seventy two hours after injury, although fatal cases have been reported in less than twelve hours. The lesser degrees of this disorder are marked by restlessness, anx iety, slight dyspnoea, accelerated breath ing, and rapid pulse. In more severe cases these symptoms become aggravated: general prostration rapidly increases; the face becomes pale and anxious; and, later, cyanosis, mental excitement, delirium, somnolence, and coma succeed each other. The dyspnoea becomes alarming, the respirations very rapid and finally stertorous. Edema of the lungs devel ops; himoptysis may occur. The pulse— weak and irregular—finally becomes im perceptible. The temperature, at first below normal, may remain so, or, accord ing to the development of secondary com plications, may rise later. Examination of the urine will reveal oil-globules float ing on the surface.
— The symptoms of fat embolism resemble more or less those of shock, ether-anaesthesia, acute septice mia, acute pulmonary and renal conges tions, cerebral haemorrhage, and embo lism. From shock it differs in that its symptoms appear so late that the symp toms of shock should have in great meas ure subsided, and in many cases where the amount of shock has not been very great from the start. The effects of ether are not easily distinguished from the ef fects of fat-embolism; the appearance of oil-globules floating upon the urine will denote the presence of fat-embolism. The symptoms of acute septicemia are developed later than those of fat-embo lism, and include a marked elevation of temperature and a more gradual develop ment; the two conditions are not infre quently present in the same case. Not in frequently the of shock, fat-em bolism, and acute septicaemia is noticed Although the symptoms of acute pulmo nary congestion are sufficiently clear, it may happen that those of fat-embolism will be confounded with them.
—Fat-embolism, to a greater or less degree, occurs in almost every fracture in adults and in operations in volving the cancellous tissue of bone. Its most severe forms are likely to be devel oped in extensive compound and multiple fractures, causing symptoms which com plicate and succeed those of shock and often resulting in death. This condition is rare in children. The conditions pre disposing to it are patent blood-vessels bathed in secretions containing liquid fat and the application of some pressure tending to force the fat into the open vessels. The local congestion and the abundant secretions poured out into the wounded tissues for several hours after an injury cause a tension of parts, which furnishes such pressure.
— The fat-globules, hav ing entered the general venous current, are carried to the right side of the heart and onward with the blood-stream into the pulmonary circulation, the finer ves sels of which they occlude, and the pres ence of the fat in which vessels gives rise to the primary symptoms. Gradually the oil-molecules are forced through the lung and pass on into the general circulation. The capillaries of the brain or spinal cord may arrest them and give rise to symp toms denoting disturbances of these or gans. The oil-molecules are, however, more frequently arrested in the kidneys and liver. The oil is excreted by the kid neys and may be found in the urine; its presence in the urine is of great diagnos tic value.