Inhaltsangabe
This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1911. Excerpt: ... CHAPTER XII THE SENSORY ORGANS AND THEIR WITNESS TO THE PROTOMITOMIC NETWORK IN turning to the sensory organs to see what evidence they afford of the underlying protomitomic network, I shall take the retina first and deal much more fully with it than with any other organ, since the comparative study of vertebrate retinas has occupied me for many years, and it was this study that yielded me the first traces of the fundamental network. The network of the retina, we shall find, throws light upon several important and interesting points. Led astray by too literal an interpretation of the shortened up processes of ontogeny, zoologists have tried to deduce the eyes of Vertebrates from the brain,1 but there can, I think, be little doubt that all the sensory organs must be deduced from the original surface of the underlying network and its fringe. Though there may still be some doubt about the retina, there 1 It seems to me that my view of the morphology of the brain and central nervous system as the residuum of the network, after all the portions destined for other organs and tissues have been abstracted, throws new light upon the ontogenetic origin of the retina. The brain is not a mass of independent cells which give up of their number to form a retina. It is merely a part of the whole reticulum from which one organ, the retina, has still to be separated. It is the interpretation of ontogenetic processes in terms of separate cells that has been the misleading element. can be none in the case of the nasal epithelium and the auditory organs, the free peripheral sensory fringe supplying us with ideal factors for the elements of these organs. Whatever its exact phylogenetic origin, the retina is one of the most instructive organs for our present purpose, not only ...
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