118 STRUCTURE, MOTIONS, REPRODUCTION. 
vious drying ; the preparations were then stained with carbol-meth- 
ylene-blue or carbol-fuchsin solution ; they were decolorized with 
nitric acid and examined in glycerin or in water. By this procedure 
the author named was able to demonstrate two kinds of corpuscles. 
One of these may be seen just inside the cell wall; it stains deeply 
with the carbol-fuchsin solution. The other lies in a position analo- 
gous to that occupied by the nucleus of vegetable cells higher in the 
scale, and resembles this both in its resting condition and in the 
process of indirect division. 
In his address before the International Medical Congress of Ber- 
lin (1890) Koch says : 
“We had not succeeded, in spite of the constantly improving 
methods of staining and in spite of the use of objectives with con- 
stantly increasing angles of aperture, in learning more with reference 
to the interior structure of the bacteria than was shown by the origi- 
nal methods of staining. Only very recently new methods of stain- 
ing appear to give us further information upon the structure of the 
bacteria, inasmuch as they serve to differentiate an interior portion 
of the protoplasm, which should probably be regarded as a nucleus, 
from an exterior protoplasmic envelope from which is given off the 
organ of locomotion, the flagellum.” 
Although usually transparent, the protoplasm sometimes presents 
a granular appearance. The botanist Van Tieghem claims to have 
found chlorophyll grains in some water bacteria studied by him, and 
in the genus Beggiatoa grains of sulphur are found embedded in the 
protoplasm of certain species. 
The granules in bacterial cells which may be demonstrated by 
special methods of staining are of two kinds: metachromatic gran- 
ules and polar granules. The former lie in the protoplasm, and 
when properly stained may present the appearance of a short chain 
of cocci lying in the bacterial cell. To demonstrate their presence 
Ernst recommends the use of L6ffler’s solution of methylene blue. 
This is placed upon a coyer-glass preparation and heated over a 
flame until steam begins to rise. After washing in water the cover 
glass is placed for a minute or two in a watery solution of Bismarck 
brown. This shows the granules stained blue and the surrounding 
protoplasm brown. The polar granules are often seen in prepara- 
tions stained in the usual way with an aniline staining solution. 
Some observers have regarded these stained granules as spores, but 
this has not been demonstrated, and cultures containing them show 
no greater resistance to heat or to chemical agents than that estab- 
lished for the vegetative cells of the particular species in which they 
are found. It seems probable that the matachromatic granules re- 
sult from degenerative changes rather than that they are reproduc- 
tive bodies. 
