STREPTOCOCCI IN COMPARATIVE PATHOLOGY. 
689 
of these commonly encountered organisms are so great that a 
method either of exclusion or of confirmation must be relied upon 
in arriving at more definite conclusions concerning the etiological 
activities of these bacteria in many of the common disorders of 
the lower animals. 
The study of the morphology and classification of bacteria 
has progressed so rapidly during the past few years that one 
finds much confusion to exist concerning not only streptococci 
infection, but streptococci themselves. It is important that such 
confusion should be avoided and that streptococci should not be 
mistaken for other genera of bacteria and vice versa. 
The genus Streptococcus is based, according to Migula,* on its 
method of reproduction or division, i.e, streptococci are spherical 
bacteria which divide in one plane. The importance of this gen¬ 
eric distinction cannot be stated until the number of micrococci 
which appear in short chains is more accurately recorded. The 
segments do not separate but are held together in short or longer 
chains, although the divisions seem to be complete. Just how 
the segments are held together is not fully determined. Accord¬ 
ing to older and more commonly encountered classifications a 
streptococcus is simply a number of micrococci (spherical bac¬ 
teria) united in the form of a chain. In some of the supposedly 
different species of streptococci the segments are often oblong 
and vary in size. Frequently, however, the segments vary in 
both size and form in the same chain. It is not my purpose in 
this paper to discuss the morphology of streptococci further than 
to call attention to certain of these different forms which are 
not infrequently encountered, and which it would seem should 
be taken into account, in their differentiation. To this end, 
I have pointed out in plate I. a number of these structural 
differences. 
The more usually observed cultural characters and bio- 
chemic properties of streptococci are quite similar, although it 
is difficult to obtain two cultures that will exactly agree in all 
cf their manifestations when grown on a large number of 
* System der Bakterien. 
