[handwritten]
3
Beyond these memoirs sections occur in medical works dealing with the subject, but adding little to the scattered material published during the last 150 years in various scientific and other journals. This material has not we believe been hitherto collected and standardized. An attempt has been made to do this in the present work, but we lay minor stress on this part of our data, because the value of the published cases is very unequal, and the family history in many of them singularly incomplete. The reporters in most cases either had not [obscured] the leisure or the inclination to pursue a lengthy enquiry of a genealogical character, and only those who have endeavoured to follow up with some completeness even a single pathological stock will grasp the amount of patience, correspondence and careful sifting required in a matter of this kind. It is a sense of the great labor involved in such inquiries, which makes us especially grateful to those ophthalmic surgeons and medical men who have provided us in many cases with most complete family histories. Their readiness to investigate, to answer further inquiries to verify individual points and follow up faint clues has given particular value to much of the new material here published, and convinced the authors how wide-spread is the tendency in the
[end]