'Wait a moment,' said Merton. 'The resources of science are not yet
exhausted. You have heard of the epoch-making discovery of Jenner, and
its beneficent results in checking the ravages of smallpox, that scourge
of the human race?'

'Oh don't talk like a printed book,' Logan remonstrated. 'Everybody has
heard of vaccination.'

'And you are aware that similar prophylactic measures have been adopted,
with more or less of success, in the case of other diseases?'

'I am aware,' said Logan, 'that you are in danger of personal suffering
at my hands, as I already warned you.'

'What is love but a disease?' Merton asked dreamily. 'A French _savant_,
Monsieur Janet, says that nobody ever falls in love except when he is a
little bit off colour: I forget the French equivalent.'

'I am coming for you,' Logan arose in wrath.

'Sit down. Well, your objection (which it did not need the eyes of an
Argus to discover) is that the patients, the lovers young, whose loves
are disapproved of by the family, will fall in love with our agents,
insist on marrying _them_, and so the last state of these afflicted
parents--or children--will be worse than the first. Is that your
objection?'

'Of course it is; and crushing at that,' Logan replied.

'Then science suggests prophylactic measures: something akin to