Aureomycin, Chloramphenicol, and Terramycin in Ophthalmology

Field: Medicine (Health Sciences)

ANIMALS DICJRNS 301Felidae and other Carnivora now introduces an addi- tional element of value-namely, stereoscopic vision, by which I mean that the images from both eyes are now beginning to be laid over one another alternately in the visual centres, first, in the external geniculate bodies, and thence via the optic radiations in the calcarine and neighbouring cortex.This factor doubtless increases the accuracy of fusion of images in depth.Development of the Hand and Thumb in Co-ordination with Stereoscopic Vision In the higher mammalian group of primates and man the importance of catching living food has disappeared, as apes and monkeys are mostly fruit eating, and man also is largely fruit eating and agricultural.There is now a more important reason for the development of stereoscopic vision of the highest type, in the increasing importance of the hand in seizing objects for inspection, and for important manual work of all descriptions requiring accurate vision.No one could watch the monkeys in the outdoor cages at the Zoo without noticing how they use the hand and vision in co-ordination for receiving and inspecting the -morsels offered to them.Though improvement in vision for hunting animal food is no longer necessary, the human hand is an immense improvement on that of the monkey, chimpanzee, or gorilla-in the development of the thumb and thenar muscles in proportionate strength and the power of opposition of the thumb to' the other fingers.By this improvement the value of the hand as a working tool acquires much greater delicacy of movement and co- ordination with vision in its manifold uses of building and of manufacturing tools, objects of vertu, and works of art of every description, as exemplified by a Michel- angelo or a Raphael in sculpture and palfnting, or a Cellini in gem making.In these arts the closest co- ordination of eye and hand is essential, but with musical instruments vision plays little part in the marvellous execution of a Paganini or an Abbd Liszt.Here the ear and memory, and the intensity of practice, take the place of vision.The monkeys and apes have concentrated on developing all four limbs with four hands, as Quadrumana, and the South American monkeys have added even a fifth "hand " in their prehensile tail, thus making an ideal machine for tree-climbing and swinging from branch to branch, and enabling them to travel long distances along the upper regions of the primeval forests without danger from carnivorous enemies on the ground.The offshoot, man, has concentrated on his fore-limb only, and by hand and vision combined-with increasing brain development, the acquisition of speech, and the discovery of fire, of agriculture, firearms, steam power, electricity, the telephone, the internal combustion motor, and, lastly, the means of flying, in ever-hastening speed of inven- tion-has gradually developed from his doubtful position as a cave man to his present supremacy in the living world.We have yet to see whether the most recent and most powerful invention, atomic fission, will be harnessed for peaceful production of power for all the nations, when all the coal and oil have been used up, or whether it will lead to the greatest means of destruction of civiliza- tion in lhistory.