A CONTRIBUTION TO THE MORPHOLOGY OF BACTERIA. 7 
plasm, we have a condition of things which does not harmonise 
with the fundamental characters of a typical bacillus, but 
rather suggests that this microbe, though under many con- 
ditions conforming with what corresponds to a typical bacillus, 
may after all not be one, or at any rate the boundary between 
it and a mycelial fungus is not a severe one. 
C. The most instructive organism, showing a similar and 
perhaps more pronounced morphological change, is the tubercle 
bacillus of Koch. As is well known, this microbe presents 
itself in the tubercular deposits and in serum and agar 
glycerine cultures in a form which has vindicated to itself 
the term of a typical cylindrical bacillus. But already in 
preparations made of the human pulmonary (tubercular) 
sputum forms occur which appear more of the character of 
threads composed of unequal—i. e. not uniform—elements ; 
some of these threads show not unfrequently a terminal element 
of the same knob-shaped or club-shaped character as those 
mentioned of the diphtheria bacilli. It was on account of 
such forms that Metschnikoff expressed the opinion that per- 
haps the tubercular bacillus is not a bacillus at all, but belongs 
to the group of mycelial fungi. I have already in 1889-90 
shown that in glycerine agar cultures of the tubercle bacilli, 
after some weeks’ growth at 37° C., there occur large numbers 
of such thread-like forms with club-shaped ends; some short, 
others long, some smooth, others made up of unequal elements ; 
further, long and short threads occur which show undoubtedly 
and markedly branchings, these latter either of great length 
or only as just commencing sprouts (see figs. 7 and 8). Thatall 
these forms are undoubtedly the tubercle parasite is shown by 
the transitional forms between the typical cylindrical tubercle 
bacilli and the long-branched threads (homogeneous or seg- 
mented), with smaller or longer lateral buddings, and by the 
fact that all these forms behave in staining (fuchsin, washing 
with nitric acid, 1:3) lke the true tubercle bacilli. I have 
seen the same forms already after three to five weeks’ growth 
on solidified hydrocele fluid; here most of the organisms were 
the typical cylindrical bacilli, but there were some undoubted 
