26
TABLE II— cont .
Number.
Description.
Combined method.
(Original and Levaditi's.)
Noguchi's method (examined
at Wellington Laboratory).
History.
Date of
examination.
Result.
Date of
examination.
Result.
1914.
1 9 1 4 .
28
V. G.O.H.
11th Dec. . . .
Positive
weak.
17th Dec. . . . Positive.
No history.
29
K. Do.
D o . . . .
Positive
moderate
Do. . . .
Negative . . .
Interstitial Koratitis. No history.
30
S.B. L.A.
Do. . . . Positive
trace.
Do. . . .
Do.
31
P. Do.
Do. . . . Positive
weak.
Do. . . .
Positive.
32
S. G.H.
Do. . . . Negative . . .
Do.
Do.
A case of dyspepsia with a history
of sore and rash two years ago.
33
R. RH.
19th Dec.
Positive
moderate.
24th Dec. . . .
Do.
34
K. Do.
Do. . . .
Do.
Do.
Do.
35
A. G.O.H.
Do. . . . Positive
strong.
Do. . . .
Do. . . .
Syphilis three years.
36
R.M. Do.
Do. . . . Positive
weak.
Do. . . .
Negative . . .
No history. Blood on 16th Nov.
1914. Positive trace : blood sent
for confirmation.
37
K. Do.
Do. . . .
Positive
trace.
Do. . . .
Positive
No history.
38
V. . . .
Do. . . .
Positive
strong.
Do. . . .
Do. . . .
Neurochoroiditis right eye.
Syphilis thirty years ago.
39
C. G.H.
Do. . . . Negative . . .
Do. . . .
Do.
40
N. Do.
Do. . . .
Do. . . .
Do. . . .
Do.
Table II shows the comparative results obtained with bloods subjected to the combined
method at this Laboratory and Noguchi's method at Wellington. Altogether 40 bloods were so
examined by both these methods. Of these 22 gave a positive result by both methods, 8 more
were positive by the combined method and negative by Noguchi's method while a farther 4 were
positive by Noguchi's and negative by the combined. Some more work on these lines is
necessary before any opinion can be arrived at.
NOTE II.—ON THE QUANTITATIVE BACTERIAL CONTENT OF NATURAL WATERS.
The quantitative bacterial content forms a test in the bacteriological examination of water.
The usual laboratory method consists in totalling up all the colonies that grow on nutrient
agar of standardised reaction incubated at blood-heat, 37°C. Definite quantities of water
under examination as 1, .1, or .01 c.c. are added to melted and cooled tubes of nutrient agar,
mixing thoroughly while still liquid, pouring out into petri dishes and allowing to solidify.
The plates are then incubated at 37°C for 48 hours ; from these the total number of colonies
in 1 cc. of the original water is calculated. This method, though it appears in theory to
afford valuable information, yet from a scientific point of view, is liable to many fallacies and
subject to many limitations. The limitations are constant features which do not vitiate the
comparative value of the test, since the colonies counted represent only those that grow under
aerobic conditions on nutrient agar of definite strength and reaction, and incubated at 37°C
for a period of 48 hours, but not the entire bacterial content of the definite quantity of water.
But the fallacies, that exist, render the test liable to give a variable result. They are :—
(1) ( a ) Sometimes it happens that solid agar sterilised in test tubes does not show any
visible growth, but on melting and pouring into plates, a number of minute colonies develop.
This is probably due to some resistent spores surviving in the depth of the agar and not
capable of multiplying under these circumstances, but, when the agar is poured into shallow
plates, favourable aerobic conditions supervene and development takes place.
( b ) The petri dishes or plates may be imperfectly sterilised and growths may develop
from the surface of the glass as soon as nutrient agar is melted and poured into them. Con
- t r o l e x p e r i m e n t s t o t e s t t h e s t e r i l i t y o f t h e a g a r s a n d t h e p l a t e s c a n o n l y g i v e p r e s u m p t i v e b u t
not definite proof that all the plates and agar tubes of the same lot are sterile.
(2)The thickness of the agar in the plate affects the growth of certain organisms, and
some colonies are missed because growth in the depth of the agar in 48 hours is too sparse to
render the colonies visible to the naked eye, whereas the same organism on the surface will
grow into fair sized colonies in that time.