Retinal structure and colour vision

Conclusion

The special feature of this paper is the dethronement of the photoreceptors — the rods and cones — from their role of absolute rulers in the visual hierarchy. The physiology of vision, especially of colour vision, was and still is too much under the spell of these structures. Remarkable as were the discoveries of the pioneers of anatomy and physiology: Thomas Young, Koelliker, Heinrich Mueller, Max Schulze, Helmholtz, Ramón y Cajal et al., in revealing the true functional significance of the rods and cones, they have on the other hand done much harm by retarding progress in the physiology of colour vision. It is now time to break this vicious circle. Extremely important as the photoreceptors are as initiators of the processes underlying vision, there is a host of other structures in the retina and in the remainder of the visual system, far too numerous and peculiarly organized to be ignored. Their numbers, the intricacy of their arrangement, their particular relationships to the rods and cones and to one another — all indicate their essential role in vision. These different bipolars, horizontals, amacrines, ganglion cells and other structures, with their numerous and different but specific contacts, are there for some definite purpose, each performing its own specific role in the function of the complex whole. It is the task of further analysis, therefore, to identify these specific functions and to assign them to particular structural constituents. This is a formidable task, but a task that promises to elevate the anatomy and the physiology of the visual organs, and of the nervous system in general, to a level to which in these times they are entitled. Then only the true significance of the detached membrane-like portion of the brain which we call the ‘retina’ will be revealed as a composite of millions of cellular individuals, every one of them a microcosmic living, working factory fulfilling its own part of the complex process. The expression ‘function’ will then not be an empty abstraction by which we try to hider our ignorance but will mean a specific activity of definite microscopic individuals and organelles. Equally so the word ‘synapse’ will acquire a new significance since it will permit you to think in terms of concrete structures which you can see under the microscope instead of those poroduced by the ‘creative imagination’. In pursuing this road, your hypotheses will be based upon firmer foundations, knowing as you will which structures exist and which do not. With me, I hope, you will agree that our further task is to subject the entire visual system including its centres in the brain to such a detailed histo-physio-chemical analysis if we ever hope to attain our goal: to bring the faculty of vision, in particular of colour vision, to our complete scientific comprehension.