Genetics and Medicine in the United States, 1800-1922 (review)

Paraphrasing Owsei Temkin’s definition of medical history, one might say that medical genetics is all of medicine that is genetical and all of genetics that is medical. Alan Rushton has written a history of medical genetics in America between 1800 and 1922. Or perhaps it should be called the prehistory of American medical genetics: the clinical specialty that is now represented by an American Board of Medical Genetics (the twenty-fourth in the family of specialty boards) and an American College of Medical Genetics is a much more recent development.

In the book’s preface, Rushton, who is a board-certified pediatrician and medical geneticist at Hunterdon Medical Center in New Jersey, says that his interest in the history of genetics was stimulated by professors at his undergraduate college, Earlham. After Earlham, he acquired the M.D. and Ph.D. (in genetics) at the University of Chicago, followed by pediatric residency training at Yale. His primary sources in this historical study were identified in The Index Catalogue of the Library of the Surgeon General’s Office, Index Medicus, and, for the interval of a few years when Index Medicus lapsed, Bibliographia Medica (Paris).

Rushton’s delving in these indices has uncovered interesting material. He points out that as early as 1845 the characteristic pedigree pattern of colorblindness was described by Pliny Earle (1809–92), a Philadelphia physician-psychiatrist. Earle illustrated his study of colorblindness in five generations of his own family with a pedigree chart representing females by circles and males by squares. Colorblindness had been first described by John Dalton (1766–1844) in himself in 1798. Color vision was physically interpreted in terms of the now-established trichromatic theory by Thomas Young in 1802, and Young’s theory was later revised by Helmholtz. It is J. F. Horner, a Zurich ophthalmologist, who is usually credited with first describing the mode of transmission of colorblindness, in 1876. The pattern was well known by 1911 when E. B. Wilson (1856–1939), Johns Hopkins Ph.D. and first professor of Biology at Bryn Mawr College later at Columbia University, assigned the first human gene to a specific human chromosome, the colorblindness gene to the X chromosome: “In the case of color blindness, for example, all the facts seem to follow under this assumption if the male be digametic (as Guyer’s observations show to be the case in man). For in fertilization this character will pass with the affected X chromosome from the male into the female, and from the female into half her offspring of both sexes. Color blindness, being a recessive character, should therefore appear in neither daughters nor granddaughters, but in half the grandsons, as seems to be actually the case.” ¹

The reason Mendel’s results of 1865 did not get more prompt attention than they did may have been that they could not draw plausibility from a knowledge of the chromosomes: the chromosomes were not discovered until 1877 (by Walther Flemming). It is not well appreciated that evidence that the chromosomes are the agents of heredity was amassed before Mendelism was rediscovered in 1900. Rushton quotes an 1886 statement by Harvard Medical School embryologist C. S. Minot, in connection with a detailed discussion of the formation of human sperm, that the chromatin within the cell nucleus is “the material substratum of hereditary transmission. . . . Chromatin is the essential factor in the fruition of heredity” (p. 35). (The chromosomes were not so named until 1888, by Waldeyer.) This is the substance of the Roux-Weismann-de Vries hypothesis, which E. B. Wilson summarized as follows: “the chromatin is a congeries or colony of invisible self-propagating vital units . . ., each of which has the power of determining the development of a particular quality. Weismann conceives these units . . . [to be] associated in linear groups to form the . . . chromosomes.” ²

In America as in Europe, dermatologists, ophthalmologists, and neurologists were early to recognize genetic disorders in their specialty. They...