For the next three years she lived with her father in London; a life
pretty evenly divided between studies and the amusements of her
world.

Dr. Derwent pursued his quiet activity. In a certain sphere he had
reputation; the world at large knew little or nothing of him. All he
aimed at was the diminution of human suffering; whether men thanked
him for his life's labour did not seem to him a point worth
considering. He knew that only his scientific brethren could gauge
the advance in knowledge, and consequent power over disease, due to
his patient toil; it was a question of minute discoveries, of
investigations unintelligible to the layman. Some of his colleagues
held that he foolishly restricted himself in declining to
experimentalise _in corpore vili_, whenever such experiments were
attended with pain; he was spoken of in some quarters as a
"sentimentalist," a man who might go far but for his "fads." One
great pathologist held that the whole idea of pursuing science for
mitigation of human ills was nothing but a sentimentality and a fad.
A debate between this personage and Dr. Derwent was brought to a
close by the latter's inextinguishable mirth. He was, indeed, a man
who laughed heartily, and laughter often served him where another
would have waxed choleric.

"Only a dog!" he exclaimed once to Irene, apropos of this subject,
and being in his graver mood. "Why, what assurance have I that any
given man is of more importance to the world than any given dog? How
can I know what is important and what is not, when it comes to the
ultimate mystery of life? Create me a dog--just a poor little
mongrel puppy--and you shall torture him; then, and not till then.