404 ABSTRACTS
IV
Various dyes were used to ascertain the effects of vital staining on T. foetus. The
effect of individual dyes was determined against various mixtures. The cytoplasm of
the organism showed twenty to thirty staining granules. The nucleus, blepharoplast,
flagella and fibrillae were only seen to take up the stain at the stage when the protozoon
was nearing death. The parabasal body, however, could not be dyed.
The time required for the taking up of dyes and their excretion by the flagellate was
found to be shortened as the temperature of the reaction was raised. The organism in
old cultures reacted negatively to vital dyes, and this was ' not only due to the acidity
of the medium but also to the functional inactivity of the protozoa '.
V
The power of oxidation and reduction possessed by T. foetus is stated by the author
to depend upon the vitality of the organism, so that flagellates of vigour and vitality
exhibit a more powerful oxidation—and reduction—ability than those in a state of
degeneration. The amount of oxydase produced was found to be directly proportional
to the reduction power.
Oxidation localities are said to be distributed in the cytoplasm, nucleus and blepharo-
plast, while the reduction localities and areas where oxydase is formed existed only in the
cytoplasm. It has further been shown by the author that in the case of a young culture
the reduction power of the trichomonads was stronger than the oxidation power, while
the opposite held true in the case of an old culture.
The presence of peroxydase in T. foetus is doubted by the author. [H. N. R.]
The relation between skin measurements and the character of swelling in
eleven hundred double intradermal tuberculin tests. J. R. RIDER (1940).
Vet. J. 96, 154-159.
T HE author has made some interesting observations on the technique of double
intradermal tuberculin test and has described the interpretation of results by a
detailed analysis of 1,100 tests performed in herds qualifying for attestation. From the
practical point of view, the author's description of the technique of the test and the
emphasis on the standardisation of the technique are of much importance.
The reading of the tests, has, as usual, been based on the character of the swellings
and their measurements ; besides a critical study has been made to correlate them in
interpreting the results. It is found that:—
(i) in over 90 per cent of cattle exhibiting swellings of the accepted negative
character (small, discrete, pea-like, without any diffusion), the increase in
skin thickness does not exceed 2 mm. at the 48th hour and the total increase
does not exceed 3 mm. at 72 hours,
(ii) in 90 per cent of the positive reactors (the criterion being diffusion, i.e. loss of
definition at the margin of the swelling), the increase exceeds 3 mm. at 48
hours and 5 mm. at 72 hours,
(iii) in the ' atypical group ' the total increase in skin thickness lies between 3
to 5 mm. About 9 per cent each of the reactors and non-reactors come
within this group.
The nature of the atypical group is discussed in detail as the character of the swelling
was either ' large negative ' or ' small positive '. So the true status of the atypical
reactors could not be definitely ascertained by a single test. In the author's opinion, it
is most likely that such reactors, after a longer or shorter interval, become definitely
positive to the test. Therefore in the interest of the herd, they have to be regarded with
suspicion.
It is also pointed out that the increase in skin thickness bears no relation to the
age or sex of the animal.
The data relating to the increase in skin measurements of the negative, positive and
a typical groups are summarised in two tables. [V. R. G.]