PYOGENIC BACTERIA. 383 
genic for rabbits only. The author named, as a result of extended and 
carefully conducted comparative studies, arrives at the following 
conclusions: 
‘* According to my observations, there are two great groups among the 
streptococci. These cannot be distinguished one from the other in cultures 
in highly albuminous media (pus, blood serum), but present constant dif- 
ferences when cultivated in bouillon. The decisive characteristics in this 
medium are: macroscopic, the cloudiness of the medium ; microscopic, the 
length of thechains. The two groups are with difficulty distinguished in 
agar cultures; more easily in gelatin, in which the streptococcus which 
forms short chains causes a slight liquefaction, while the Streptococcus 
longus does not. Upon potato Eareptocoocus brevis alone shows a visible 
growth. . . . Wesee here a group of streptococci which we separate from 
the others, because of their microscopic and cultural differences, under the 
name of Streptococcus brevis, which is also distinguished by having no 
pathogenic action upon the animals usually experimented upon. We 
recognize, on the other hand, the streptococci which we have grouped to- 
gether as Streptococcus longus as all pathogenic and about in equal degree 
for a certain species of animal (rabbits); but by experiments upon other 
species (mice) we arrive at the conclusion that there must also be differences 
between these streptococci. It appears that the streptococci which are dis- 
tinguished by their high degree of pathogenic power upon mice are also 
those which are distinguished in bouillon cultures by the formation of con- 
glomerate masses. We find among these also one which is distinguished 
by especial virulence for mice, and that this one is distinguished in cultures 
by its scanty growth upon ox serum.” 
The more recent researches of Knorr (1893), and of Waldvogel 
(1894), indicate that the classification of the streptococci proposed by 
von Lingelsheim has no great value, and show that marked changes 
in biological characters and in pathogenic power may result from 
cultivation in special media, or from successive inoculations into 
animals. 
Morphology.—Spherical cocci, from 0.4 4 to 1 « in diameter, but 
varying considerably in dimensions in different cultures, and even 
in asingle chain. Multiply by binary division, 
in one direction only, forming chains, in which 
the elements are commonly associated in pairs. 
Under certain circumstances, instead of form- 
ing chains, a culture may contain only, or 
chiefly, diplococci ; but usually chains contain- 
ing from four to twenty or more elements are 
formed, and these are frequently associated 
in tangled masses. Occasionally one or more 
cells in a chain greatly exceed their fellows in 
size, and some bacteriologists suppose that Fie. 8—Pus containing 
these cells serve as reproductive spores—arthro- Hoa eee 
é ‘ igge.) 
spores—but this has not been definitely proven. 
Stains readily with the aniline colors and by Gram’s method. 
