She was just in time to pick up the blind, whimpering thing.

The driver of the tram, seeing Mary in its path, put on the brakes sharply.

The tram lumbered to a stoppage, but not before Mary had been flung down on her face and her arm broken by the hoof of the horse nearest her.
It was likely to be an uncommonly awkward thing for the Gray household, seeing that it was Mary's right arm that was injured.

For one thing, it would involve the dispossession of that year's baby.

For another, it would put Mrs.Gray's capable helper entirely out of action.
When Mary was picked up, and stood, wavering unsteadily, supported by someone in the crowd which had gathered, hearing, as from a great distance, the snarling and scolding of the tram-driver, who was afraid of finding himself in trouble, she still held the blind and whimpering dog in her uninjured arm.
She wanted to get away as quickly as possible from the crowd, but her head swam and her feet were uncertain.