508 THE ANAEROBIC BACTERIA 
organisms, however, of the anaerobic type appear to be accUmated 
to either a parasitic existence upon hving hosts or a pathogenic exist- 
ence within the tissues of the host. The anaerobic bacilH, on the con- 
trary, are for the most part "opportunists" with reference to infection. 
In general, therefore, it may be said that sporulating anaerobic 
baciUi are inhabitants of the ahmentary tracts of mammals, and they 
are found in the spore state in the soil. This does not preclude the 
possibility of a vegetative existence in the soil in symbiosis with facul- 
tatively anaerobic organisms. 
Prior to the World War, the anaerobic bacteria were for the most 
part but little studied, except the few forms which produce potent 
soluble toxin, as B. tetani and B. botulinus, or those which incited 
specific disease in animals, as the Rauschbrand bacillus. 
One of the great discoveries of the war was the unfolding of the part 
played by the anaerobes in the causation of that deadly infection known 
as gas gangrene. Isolated cases of "foamy organs" and emphysema- 
tous gangrene were recognized from time to time in civil life, but the 
enormous importance of bacteria in the causation of this condition is a 
distinct war contribution to medical science. 
The single greatest development, aside from the etiological relation- 
ships, has been the complete overturn of the anaerobic procedure. 
Practically all prewar descriptions of anaerobes have been shown to be 
inaccurate; the remarkable symbiosis between widely different types 
of bacteria, as the Welch bacillus and B. sporogenes, have been dis- 
covered; the extreme inadequacy of ordinary methods of plating or 
similar procedures as a means for obtaining pure cultures has been 
exposed, and an entirely new literature will have to be laboriously 
accumulated before the anaerobic bacteria can take their place in bac- 
teriology on a parity with the typhoid bacillus, the tubercle bacillus 
or B. coh. 
The extensive investigations of the British IVIedical Research 
Committees, and of Weinberg and Seguin, deserve special mention as 
being pioneer work in the newer bacteriology of the anaerobic bacilli. 
ISOLATION AND CULTIVATION OF ANAEROBIC BACTERIA. 
Numerous investigations of anaerobic bacteria, especially those of 
importance in wounds of warfare, have shown that pure cultures of 
such organisms are extremely difficult to obtain, and to maintain. 
Published descriptions of anaerobic bacilli, even those of B. tetani 
and B. botulinus, show definitely that at least two, possibly more, 
organisms have been frequenth' culti^'ated and kept as "pure mixed 
cultures." The symbiosis of anaerobic bacteria, indeed, is one of the 
striking developments of the study of this group. Ordinary plating 
methods are generally unreliable for the isolation of pure cultures of 
the anaerobic bacilli, but the "spiral streak" method of Varney (see 
below) has been found satisfactory. One other procedure which can be 
