I am sorry to have overlooked your review of McCarty's book until now. Thank you for it! You know how important the
Avery et al (1944) paper was to my own outlook.
May I enlarge on your remark about Griffith's understanding of his own discovery? He gave a labored (and murky) rationale
for having done the experiment. But unlike many followers he did understand the differences between gene and product: see
the enclosed excerpt. Don't fault him for saying protein for DNA!