On the growth of the crystalline lens / by Priestley Smith.

  • Smith, Priestley.
Date:
1883
Catalogue details

Licence: Public Domain Mark

Credit: On the growth of the crystalline lens / by Priestley Smith. Source: Wellcome Collection.

Provider: This material has been provided by Royal College of Physicians, London. The original may be consulted at Royal College of Physicians, London.

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    Reprinted from Vol. HI of the Op k that mo log ical Society's Transactions.'] a. ,u~—■. h -u~ % ON THE GROWTH OF THE CRYSTALLINE LENS. By Priestley ^Smith (Birmingham). The present position of knowledge concerning the growth of the crystalline lens cannot, I think, be stated more concisely, or on better authority, than by quoting a passage from the chapter by Otto Becker in the Handbook of Graefe and Saemisch. “ In the new-born child the lens is smaller than in the adult, and of a more globular form; it is clear as water, very soft, and nearly equally soft in all its layers. The comparison as to size is true, however, only of the equa- torial diameter, for according to Jaeger the antero-poste- rior diameter is equal, or very nearly so, to that of the adult lens. The changes which take place during life are referable to two opposing processes. “ So long as the whole individual grows, that is up till about the twenty-fifth year, new lens-fibres are laid down at the equator and apply themselves, as they further develop, to the anterior and posterior surfaces, each fibre bending .round the equator. Hence the lens continually increases in its transverse diameter, and gradually loses its spherical form. The addition of the new fibres at the equator has little influence on the thickness of the lens, because it is only when the fibres have attained their maxi- mum length that they reach to the poles. Thus the sur- faces of the lens assume a flatter curvature and the diop- tric power diminishes. “ The slight increase in thickness which would never-