He only suffered a certain limited and unimportant part of him to be made into a machine.
Meanwhile it was perhaps in the divine mercy that the workings of this machine were hidden from Isaac.

He hadn't even found out that the secret spring was not in the brain but the heart of it.

He would look up a little uneasily as Keith pushed through the big swinging doors and took his seat at the table on the platform, and while he wondered what Keith was thinking of him, ten to one Keith wasn't thinking of him at all.
This morning, however, he _was_ thinking of him, as it happened.

And when the old man saw him up there, holding his poor bursting head in his hands, and said: "'Ead achin' my boy, again?
That comes of studyin' too 'ard!" he thought with a touch of compunction, "What would he say if he knew I'd gone drunk to bed last night?
And if he knew about Poppy ?" Isaac approached his son gingerly and with a certain fear.

The only thing he had discovered about this admirable machine of his was that it went better when you left it alone.