1919] on A Filter-passing Virus in Certain Diseases 557 



The results of the work carried out at Staples may be surumarized 

 as follows. Filter-passing organisms have been isolated by culture 

 from the blood and from the secretions of the body in a considerable 

 number of diseases of obscure origin, and these organisms fall into 

 two definite groups. The first and smaller group consists of those 

 entitled to be called globoids, and the second and much more 

 numerous group is that of the true filter-passers. The so-called 

 globoids are characterized especially by the fact that on staining 

 they show a distinct differentiation into a central darkly staining and 

 a peripheral less stainable zone. The latter has often a somewhat 

 indefinite outline, so that it is difficult to separate with sharpness one 

 individual from its neighbours. The non-globoid filter-passers are, 

 on the other hand, extraordinarily sharply defined, although often 

 extremely minute. The different members of this series present 

 individual morphological differences not only of size, but also of 

 shape and arrangement. Thus some are rounded, others oval ; some 

 form short chains of three or four individuals, others are arranged in 

 pairs ; others form a mosaic-like pattern. They also present differ- 

 ences in their culture— not only differences in the ease or difficulty 

 of growth in the Noguchi medium, but also differences in the rate 

 and mode of growth. 



The organism isolated in rabies is the smallest we have as yet 

 seen : it is in the form of a minute very sharply defined rounded body, 

 varying in size from O'l fx to 0'3 /x in diameter. The organism of 

 influenza is also very small, measuring 0'15/>tto0*5/>i; it also has 

 a very definite outline, and is a minute rounded or oval coccus-like 

 body. The organisms of trench fever and of nephritis are distinctly 

 larger, the former varying from * 3 /x to • 5 //, and the latter from 

 • 3 /x to • 6 /I.. Speaking roughly, they are two to three times the 

 size of those found in rabies or influenza. The organism of trench 

 fever is very definitely paired, each member of the pair consisting of 

 a minute oval coccus-like body, and the surfaces opposed to each 

 other are flattened — this produces a very typical picture under the 

 microscope. The organism isolated in nephritis is rather larger, 

 varying from ' 3 /x to • 6 /x ; it also is an oval coccus-like body, 

 arranged usually in twos or in fours, and quite often in the form of 

 short chains of four individuals. None of these four organisms show 

 any differentiation on staining — no separation of an inner and an 

 outer zone ; but in some, as, for instance, in the organisms of trench 

 fever and of nephritis, there is sometimes in cultures a suggestion of 

 the presence of a capsule. This, however, is not confirmed either by 

 staining or by dark-ground illumination. The organisms isolated in 

 polyneuritis and in encephahtis are definite globoids varying in size 

 from • 2 /x to • 5 /x. It may be useful to compare the size of these 

 organisms with that of the better known bacteria. 



It may be said that the average bacterium is approximately 

 2 fjL long and 0*5 /x in diameter. One of the smallest organisms 



