=9. Air Embolism.=—The fault of introducing air under the skin with the syringe at the time of injection can only be the result of flagrant negligence. Every physician should know enough to hold the syringe in an erect or vertical position, and to expel the air above the solution in his syringe, as is done with any hypodermic injection. Air embolisms are also occasioned by a careless filling of the syringe with the hydrocarbon in a cold state, as the material is now generally used, and while the dangers of such emboli are very much exaggerated they should not be permitted, when by the pouring in of the liquefied material the syringe can be filled evenly. Practically there is no harm done by the injection of air under the skin, yet it elevates the skin at the site of the defect and hinders the surgeon in accomplishing the best results. These emboli cause a bulging up of the skin for the time being and may occasion more or less pain to the patient, which passes away in ten or twelve hours, leaving the parts as injected except for such reactionary symptoms or edema, already referred to. =10. Paraffin Embolism.=—The creation of an embolism is invariably due to an injection of the foreign substance directly into a blood vessel. This condition is one of the most objectionable, if not the most dangerous, factor associated with the subcutaneous injection of any foreign matter, be it a liquid substance, as, for instance, an oil; many cases have been placed on record where they have been observed after the introduction of even paraffin of high melting points, when introduced under the skin in hot liquid state. Consequently the use of vaselin liquefied by the aid of heat is especially liable to give rise to such condition. Pfannenstiel cites a case wherein he injected paraffin in which the patient was at once attacked with violent coughing, and for three days exhibited symptoms of grave nature, such as pain in side, intense dyspnea, acceleration of the pulse, hyperthermia, cyanosis of the face, hemoptysis, violent cephalalgia, and vomiting—all indications of pulmonary and cerebral embolism. The injection in this case was one of 30 c.c. of paraffin, with a melting point of 45° C. The symptoms as mentioned continued for about one week, gradually subsiding, and followed by recovery. Kapsammer has also noticed such symptoms. Leiser, after injecting vaselin to correct a saddle nose, noted an immediate collapse of the patient, which was obviated only by the hypodermic use of ether and the resort to artificial respiration. When the patient returned to consciousness, he was found to be entirely blind in the right eye, the eye before the operation having been known to show only a pronounced astigmatism. Kofman cites the loss of a patient from the injection of 10 c.c. of paraffin for vaginal prolapsis. Moskowicz observed two cases of pulmonary embolism treated in the same manner, stating that an alarming dyspnea continued for several hours.