His reason for choosing these cells for his experiments is that they are a well-spring of life.
Out of the heart are the issues of life, and within, it is life's well-spring.
It is the well-spring of the heart,—the Castaly of the soul.
She was a well-spring of joy in the house, and we all loved her.
And this outflowing is the fulness, more or less, of the soul's well-spring ...