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2 THE MICROORGANISMS OF THE HUMAN MOUTH.
plants which have leaves, stems, and often also roots. These
represent a higher stage of development than the Thallophytes,
inasmuch as the latter do not have the parts mentioned.
Thallophytes are very commonly divided into Fungi, Algse,
and Lichens: Fungi being characterized as cells witlioat chloro-
phyl, which subsist on preformed organic substances: Algte as
cells wltk chlorophyl, living on inorganic substances ; Lichens as
a combination of cells with and without chlorophyl, also living
on inoro;anic substances.
This classification has, however, recently been justly pro-
nounced untenable, since it is not possible to make the presence
or absence of chlorophyl a criterion for determining the fungal
or non-fungal character of any growth. The fungi comprise not
only Thallophytes without, but also such with chlorophyl, and
indeed some of the most characteristic members of this group
of Thallophytes contain chlorophyl (deBary^). Secondly, fungi
and algse show so marked a similarity in regard to their mor-
phology and conditions of reproduction, that a separation on the
chlorophyl basis alone scarcely seems desirable. In the third
place, recent investigations have demonstrated with considerable
ocrtaintv that lichens are not entitled to recognition as a sepa-
rate group of organisms, being nothing more than a mixture of
fan""i and algse, in which the formar live as parasites upon the
latter (Fliigge"). Again, the view^ has been steadily gaining
ground that bacteria have very little in common with the pure
fui\o-i, and accordingly should not be classed with them.
For the present I have, however, retained the old division,
particularly as the question of arranging and classifying the
'i'hallophvtes has not yet been definitely settled. (See Lit.
1,2,3,4.)
From a hygienic point of view we recognize four chief groups
of fungi
1. Fission-fungi (Bacteria) . . . Schizomycetes.
2. Mould- or Thread-fungi (Fungi proper,
Moulds) Hyphomycetes.
3. Bud-fungi (Yeast-fungi, Yeast) . . Blastomycetes.
4. Animal-fungi (Pilzthiere) . . Mycetozoa.
2 THE MICROORGANISMS OF THE HUMAN MOUTH.
plants which have leaves, stems, and often also roots. These
represent a higher stage of development than the Thallophytes,
inasmuch as the latter do not have the parts mentioned.
Thallophytes are very commonly divided into Fungi, Algse,
and Lichens: Fungi being characterized as cells witlioat chloro-
phyl, which subsist on preformed organic substances: Algte as
cells wltk chlorophyl, living on inorganic substances ; Lichens as
a combination of cells with and without chlorophyl, also living
on inoro;anic substances.
This classification has, however, recently been justly pro-
nounced untenable, since it is not possible to make the presence
or absence of chlorophyl a criterion for determining the fungal
or non-fungal character of any growth. The fungi comprise not
only Thallophytes without, but also such with chlorophyl, and
indeed some of the most characteristic members of this group
of Thallophytes contain chlorophyl (deBary^). Secondly, fungi
and algse show so marked a similarity in regard to their mor-
phology and conditions of reproduction, that a separation on the
chlorophyl basis alone scarcely seems desirable. In the third
place, recent investigations have demonstrated with considerable
ocrtaintv that lichens are not entitled to recognition as a sepa-
rate group of organisms, being nothing more than a mixture of
fan""i and algse, in which the formar live as parasites upon the
latter (Fliigge"). Again, the view^ has been steadily gaining
ground that bacteria have very little in common with the pure
fui\o-i, and accordingly should not be classed with them.
For the present I have, however, retained the old division,
particularly as the question of arranging and classifying the
'i'hallophvtes has not yet been definitely settled. (See Lit.
1,2,3,4.)
From a hygienic point of view we recognize four chief groups
of fungi
1. Fission-fungi (Bacteria) . . . Schizomycetes.
2. Mould- or Thread-fungi (Fungi proper,
Moulds) Hyphomycetes.
3. Bud-fungi (Yeast-fungi, Yeast) . . Blastomycetes.
4. Animal-fungi (Pilzthiere) . . Mycetozoa.
