The principles of physiology / by John Gray McKendrick.

  • McKendrick, John Gray, 1841-1926.
Date:
[1912]
Catalogue details

Licence: Public Domain Mark

Credit: The principles of physiology / by John Gray McKendrick. Source: Wellcome Collection.

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    that of the feeblest tone that can be heard by the ear at the same distance ; one part of sul¬ phate of quinine can be detected in 1,000,000 of water ; the odour of one part of bromine, and even much less of iodoform may be de¬ tected in 1,000,000 of air. Possibly the senses of some animals are even more delicate. 132. Each organ of sense has accessory apparatus suitable to it. Thus the eyeball is a camera for the purpose of forming, in accord¬ ance with the laws of dioptrics, an image on the retina. Vibrations of sound are conveyed to the internal ear by a complicated conducting mechanism of a drumhead, a chain of bones, and reach a delicate organ in the cochlea, known as the organ of Corti. By hair-like processes in the semi-circular canals of the inner ear, acted on by pressures of fluid in the canals, varying according to the position of the head, we appreciate the position of the head in space, and we regulate the move¬ ments of the body accordingly. In the tongue and nose there are special epithelial structures, such as the taste bodies and the olfactory epithelium acted on by odoriferous