_The Pseudo-diphtheria Bacillus._[97] Löffler and Hoffman described a bacillus having the same morphological characters as the true _Bacillus diphtheriæ_, except that it had no virulence. Roux believes this is merely an attenuated diphtheria bacillus. It is frequently found in healthy throats. The chief differences between the real and the pseudo-bacillus are: 1. The pseudo-bacillus is thicker in the middle than at the poles, and not so variable as the _Bacillus diphtheriæ_. Polar staining is absent. 2. Its growth on potato reveals cream-coloured colonies visible in a couple of days; the real bacillus is invisible. 3. The pseudo-bacillus will not grow at all anaërobically in hydrogen, but the _Bacillus diphtheriæ_ is able to do so. 4. There is the great difference in virulence. +Suppuration.+ This term is used to designate that general breaking down of cells which follows acute inflammation. An "abscess" or "gathering" is a collection, greater or smaller, of the products of suppuration. The word _pus_ is generally used to describe this matter. We may have such an advanced inflammatory condition in any locality of the body, and it will assume different characters according to its site. Hence there are connected with suppuration, as causal agents, a variety of bacteria. Pus is not matter containing a pure culture of any specific species, but, on the contrary, is generally filled with a large number of different species. The most important are as follows: 1. _Staphylococcus pyogenes aureus._ These are micrococci arranged in groups, which have been likened to bunches of grapes. They are the common organisms found in pus, and were with other auxiliary bacteria first distinguished as such by Professor Ogston, of Aberdeen. There are several forms of the same species, differing from each other in colour. Thus we have the _S. pyogenes aureus_ (golden yellow), _albus_ (white), _citreus_ (lemon), and others. They occur commonly in nature, in air, soil, water, on the surface of the skin, and in all suppurative conditions. The _aureus_ is the only one credited with much virulence. It occurs in the blood in blood-poisoning (septicæmia, pyæmia), and is present in all ulcerative conditions, including ulcerative disease of the valves of the heart. The _Staphylococcus cereus albus_ and _S. cereus flavus_ are slightly modified forms of the _S. pyogenes aureus_, and are differentiated from it by being non-liquefying. They produce a wax-like growth on gelatine.