In cases where, from long-continued disease and the repeated introduction of vitiated fluids into the circulation, the blood has lost its power, there appears no reason to doubt the correctness of Dr. Sédillot's observations; and it is probable that pus-globules may then circulate with those of the blood. In experiments upon animals, it has always been found that the power of the constitution, in resisting the effects of the injection of pus into the veins, was much greater at the first than at any subsequent operation. This circumstance would appear to associate itself directly with the observations now made, and to afford another illustration of the power of healthy blood in resisting the entrance of some foreign matters into the system. From the consideration of these facts, and of the experiments previously recorded, it becomes evident, that the introduction of pus into the system through an injured or inflamed vein, can rarely be the first step towards purulent infection of the system. Some change must previously have passed in the blood, by which its coagulating power is impaired, or some unusual mechanical means must have been employed, before the pus can find its way in the course of the circulation. The contradictory statements which have been made by those who have injected pus into the veins, may thus be reconciled, by taking into account the power exercised by the blood in the experiments which have been made. There can be little doubt that, while, in some instances, a portion of the pus has been forced into the general circulation, in the great majority of cases it has been detained in the vein into which it was first introduced, and has never become part of the circulating fluid. We accordingly find some experimenters recording the secondary diseases which they observed, while in other hands these appearances were not produced. Dr. Sédillot[30] has attempted to prove that the globules, or solid parts of pus, must be introduced into the system, in order to produce well-marked indications of purulent infection. But this hypothesis would not only appear to be at variance with the oft-repeated experiments of MM. Gaspard and Cruveilhier, in which similar effects were produced by the injection of mercury and of putrid fluids, but would also leave unexplained the mode of the introduction of these globules, where there is evidence that the disease has been communicated through the lymphatic system. The changes which all substances undergo in their passage through the absorbent glands, would at once forbid the idea that globules of pus could be thus introduced unchanged into the circulation; and yet we have direct evidence (Case XXIX) that irritating fluids are conveyed in this way into the system, and lead to the formation of secondary abscesses.