September, 1951]
AMRITAMOY
MUKHERJI
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finally manifested in the resulting immunity acquired by the animal. The precise
nature of modus operandi of any single factor is, however, not known. When the
animal is exposed to the sun, the superficial blood vessels are dilated and the tempera-
ture of dermis and deeper layers of tissues is raised; the heart beat and respiration
count are increased and consequently the circulation of blood becomes rapid. The
heated blood from the peripheral vessels, while passing through the internal organs,
also raises the temperature of the latter and this process of 'heating up of the body'
continues during the period of exposure to the sun. This action is purely physical.
In this process, it is very likely that the functional activity of first-line defence
mechanism, which consists of lymph glands, becomes impaired and the lymphocytes,
which originate from these glands and are regraded as the precursors of the anti-
bodies, also get inactivated. In the exposed animals, histiocytes and reticular
cells, which are so plentiful in the dermis and other tissues beneath it, are probably
inactivated due to the exposure to the solar radiation. Therefore, their response
to the antigen becomes weaker, as a result of which less number of antibodies are
formed. Reverse is the case in the 'Shade group' animals which were kept in a
cooler environment and due to this, the histiocytes and reticular cells probably
responded more satisfactorily to the antigen with consequent release of more number
of antibodies in the circulation. In all cases, the passage of the antigen from the
primary site of infection to the blood stream is mainly by way of the lymphatics and
the histiocyte depots in the regional lymphatic glands play a prominent part in the
retention and subsequent release of the antigen, altered or unaltered, into the
circulation. The injected antigens at this stage are probably further attenuated
and it is likely that this is accompanied by partial loss of their antigenic properties.
When the body temperature is cooler, certain physiological changes take place.
Under this condition, the endocrinal secretions, more specially those of thyroid,
pituitary and adrenals, are augmented and reverse is the rule when the body tempera-
ture gets hotter. Therefore, the rate of 'lymphocytic—dissolution' which is
under the control of the pituitary—adrenal secretions, is retarded due to the di-
minished secretions of these glands when the animal is exposed to the heating effects
of the solar radiation. It follows that more antibodies are released from the
'lymphocytic dissolution' while the animal is kept in a cooler environment, and
comparatively less number of antibodies are released due to the same process when
the animal is kept in a better environment. The results obtained by the series of
experiments conducted by the author also fully corroborate this hypothesis. In
the Staphylococcus toxoid experiment (incorporated in Part I), and in the three out,
of four rinderpest experiments, the antibody concentration of the blood of the
'Sun group' was found to be lower than that of the 'Shade gruop' which was kept
as control in a cooler environment. The difference between the potency of the two
lots of immune sera, one from the 'Sun group' and the other from the 'Shade
group', was found to be highly significant in the majority of the tests. In the
fourth experiment of the rinderpest the potency of sera of both the groups was
calculated as zero. If the fallacy of the calculation is ignored for the moment and
due attention is paid to the protective power of immune serum, then the fact stands
out that while all the 6 hill-bulls, which received 'Sun group', serum died of rinder
pest, in the lot which received 'Shade-group serum', 4 died of rinderpest but the
other 2 survived. The environmental temperature under which the immunized
hill-bulls of the 4th experiment lived was much hotter than that under which the