In 1849, Henry Gray wrote An Essay on the Origin, Connections, and Distribution of the Nerves of the Human Eye, and its Appendages; illustrated by Comparative Dissections of the Eye, of other Vertebrate Animals. Although the nearly 400-page text won the Royal College of Surgeons’ Collegial Triennial Prize of 50 guineas, it was never published or reproduced. Some of his dissections still exist, but many were destroyed in World War II bombings. While Gray's Anatomy, first published in 1858, is a classic of general anatomy textbooks, his Essay is virtually unknown. The retina section of the latter work is the main focus of this article.
The son of a private messenger for King George IV and for King William IV, Gray was a prize-winning student in anatomy at St. George’s Hospital and soon was named demonstrator and lecturer of anatomy, post mortem examiner and curator of the Pathological Museum and then house surgeon. He was a fellow of the Royal College of Surgeons and later of the Royal Society. His extensive study of the spleen won the Astley Cooper Prize of 300 pounds. After contracting smallpox from his nephew, Gray died in 1861.
His ground-breaking ocular studies were hampered by difficulties with thin tissue sections, staining, and fixatives. It was frequently the case that the retinal tissue was macerated with needles. The various fragments were observed and then pieced back together like a mental jigsaw puzzle. This led to various theories about the layering of the retina and from where the different granules and pieces originated. A favored theory at the time was that the retina and brain were one single nerve that had different layers and forms, mostly without cell membranes. No one, including Gray, had seen a synapse at that time. The visual functions of the different layers were basically mysteries. Gray wrote, “The way by which such sensation is produced, or transmitted, is and I think ever will remain an enigma, too subtle for our intellect to unravel.”
He placed the origin of the retina in a serrated border posterior to the ciliary processes, rather than more anterior, as others claimed. He assigned the pigment epithelium to the choroid and described its relation to the retina thus: “I have never however been able to trace any connection as has been described by ‘cellular tissue and vessels’; between these two layers, the two membranes appear to be in simple apposition.”
Gray felt Jacob’s membrane (rods) was a single epithelial layer possibly of the same nature as a serous membrane. Microscopically, the rod outer surface resembled “beautifully regular closed pavement.” He clarified that many previously described irregularities at their free ends were artifacts. Importantly he found smaller bodies of an oval elongated nature, which he proposed to be nucleated rods in an early stage of development. However, he mentioned that William Bowman considered these bodies a separate group, which he called “bulbs.”
Before Gray became a member of the Royal Society of London, Bowman presented a portion of Essay concerning the embryology of the chick eye in 1850. A contemporary reviewer wrote, “Although Mr. Gray’s paper wants completeness on some points, yet it is a highly valuable contribution to our previous knowledge, and promises well for the future eminence of an observer, who is, we believe, just out of his pupilage.”
Note from the author: I wish to express my appreciation the assistance Ruth Richardson, MD, in preparation of this article, especially in the retrieval of the only copy of the original ophthalmic document by Henry Gray, which is in the library of the Royal College of Surgeons in London.
For more stories from Scope, download the winter 2017 issue (PDF 720K)