Pyemia is only met with in connection with suppuration, as far as known, never without it. In those cases which appear to be free from suppuration pus will be found. _Pyemia may be described as septicemia plus thrombotic and embolic accidents, which lead to distribution of infectious material to all parts of the body._ This distribution is made by the bloodvessels, although to some extent the lymphatics undoubtedly participate. When pyogenic organisms reach bloodvessel walls they tend to set up a _mycotic phlebitis_, which, by virtue of the coagulating blood, becomes soon what is known as _thrombophlebitis_. Infection proceeding through the vessel walls, the endothelial lining is loosened, while to these rotting spots leukocytes adhere and coalesce into a more or less homogeneous mass. This so-called _white thrombus_ becomes also infected with bacteria; portions of it, loosened and dislodged, are carried by the returning blood stream to the right side of the heart, whence they are distributed through the lungs. Dislodgement may be made by mere force of the blood stream, or may be assisted by movements of the part or handling of the same. These particles of thrombi are loaded with the infectious organisms which began the disease, and wherever one settles a reproduction of the original thrombophlebitis is rapidly produced. In this way numerous infected thrombi are formed within the vessels of the lungs, which, again, loosen, and are now swept into the left side of the heart, whence they are distributed with arterial blood in all directions. While it is true that they are equably distributed, it is also positive that certain tissues seem more capable of lodging and being attacked by the contained organisms than are others. When it is once appreciated that each particle of infected clot is capable of setting up, either in the lungs or in the other tissues, upon the second distribution, other abscess formations analogous in etiology to that from which came the first disturbance, then the fundamental idea of _metastatic abscess_ is fully impressed. The term _metastasis_ may be regarded as _synonymous with transportation_, and metastatic abscesses are those produced by transportation of infected particles from one part of the body to another. Wherever they lodge similar trouble will result. Contiguous minute metastatic abscesses quickly _coalesce_, and in this way large collections of pus are formed. The blood also contains organisms not attached to thrombi, and from the blood of the pyemic patient cultures can at almost any time be made. Until this is done it will be virtually impossible to incriminate any particular organism as the one at fault. _Thrombo-arteritis_ is the equivalent in the arteries of thrombophlebitis in the veins, and is accompanied by the same detachment of endothelium, adhesion of leukocytes, etc. Whenever such a lesion occurs in artery or vein, coagulation necrosis takes place and suppuration occurs around it.