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the organisms No. 69 and cloaæ. If the above theory were correct, Grunthal should
have survived No. 69 and cloaæ, as neither of the latter were obtained at the start.
Experiments Nos. 26, 31 and 34 all show that the grunthals kept about the same
f o r t h e f i r s t f e w a n a l y s e s , b u t p r e d o m i n a t e d a t t h e e n d , t h e r e b e i n g n o g r e a t n u m e r i c a l
superiority at the commencement in these cases.
As regards Experiment No. 27: The composition before exposure in Experiment
No. 18 is almost identical with that of No. 27 (coscoroba greatly predominating), yet
in spite of this numerical superiority to start with, this organism did not survive at the
e n d t o t h e e x c l u s i o n o f o t h e r o r g a n i s m s , b u t f e l l o f f i n n u m b e r s , a n d w a s a t t h e l a s t
analysis entirely outnumbered by cloacæ, bacillus grunthal also being present—neither
of which organisms were represented in the first analysis. So that taking all the
sunlight experiments together they disprove the truth of the above explanation.
If further proof be necessary, the following points are quite convincing: (1) in
Experiment No. 1 the preponderating organism was soli communis; it disappeared.
entirely before the second analysis was taken, and never reappeared; (2) in very few
of the emulsions before exposure is bacillus cloacæ shown to be present. In nearly
every sample bacillus cloacæ appeared later on, persisted for a certain length of time,
and either remained to the end or disappeared just before bacillus grunthal. These two
important facts are, we consider, sufficient to dispose of a general assumption that the-
predominating bacillus in an emulsion at the commencement of an experiment will,
other things being equal, be the last to survive.
Before finally leaving this subject we wish to emphasise, what has already been
laid down, viz., that we do not state that there is a perfectly fixed degree of power of
resistance to sunlight in all specimens of any one species, but simply, that a certain
proportion of one organism resist sunlight longer than a certain proportion of another,
both being placed under similar conditions. The explanation of the behaviour of
the grunthal group in Experiments Nos. 28 and 32 has also been quite recently
discovered. By the use of the new Benzaldehyd test for indol (inability to obtain the-
necessary reagents accounting for the delay) we have sub-divided the bacilli included
in the term "Gunthal" (vide table III, Nos. 4, 5, 7) into two, one indol + and the.
other indol—. The farmer is a more susceptible, the latter a more resistant organism.
Unfortunately no indol reaction was done in Experiments Nos. 28, 32, but this seems.
a probable explanation of the result obtained.
It will be noticed that there is little or no difference between the results..
obtained with cowdung and human faces. This is after all what one would expect;
for the accumulation of our knowledge of fecal organisms all tends to show that no
difference whatever can be found between the same organisms derived from
the intestinal tract of a great variety of animals.
We therefore consider that the following broad conclusions are justifiable from
this series of experiments, in spite of the somewhat small amount of work done;
the subject is still being carefully studied
: —
(1) that the sun has a very powerful action in destroying all fœcal organisms
in water, particularly when they are "naked" and not surrounded by mucus derived
from the intestine;
(2) that all fecal organisms do not possess the power of resisting the action of
sunlight to an equal degree;
(3) that it is possible to divide fcal organisms, with a reasonable degree
of accuracy, into the following classes:—
(i) The delicate organisms or those that are very susceptible to the action
of the sunlight (vide the remarks on Coli commums);
(ii) An intermediate class containing a very large number of organisms which
occupy an intermediate position between the two extremes; and
(iii) The resistant organisms or those capable of resisting the action of sun-
light for considerable length of time (vide the remarks on Cloacæ,
Grunthal, etc.).
It is not pr of osed to discuss the position of any particular species of organisms
in these three classes, until the conclusions arrived at in the further work on this
subject have been considered.