VITAL STATISTICS. 



11(1!) 



was presbyopie for horizontal lines and 

 myopic for vertical. This he remedied by 

 rearing spectacles the glasses of which were 

 cyliiulrie bi-convexes, with rectilinear, hori- 

 zontal anil similar axes. These glasses obvi- 

 ated the presbyopia relative to the horizontal 

 lines, and they were combined with sphero- 

 biconcave lenses to get rid of the myopia for 

 vertical lines. Each of the glasses was made 

 moveable for facility of cleaning. 



The following means are recommended to 

 ascertain if an eye has the defect now de- 

 scribed. The person should attentively con- 

 template for some time and with attention a 

 cross, three or four lines in size, made of fine 

 wire and fixed in a frame. If affected, he 

 will see the horizontal lines differ in thickness 

 and blackness of tint from the vertical. 



To determine the focal length which the 

 lenses should have, a person whose sight is 

 presbyopia in one direction should take bi- 

 sphero-convex lenses which enable him to see 

 distinctly at the ordinary distance the lines 

 which otherwise appear indistinct: he can 

 deduce the focal distance of the cylindrico- 

 convex glasses. A person myopic in one 

 direction should do the same with regard to 

 bi-sphero-concave lenses. The convex glasses 

 should be chosen of one or two numbers 

 stronger. 



BIBLIOGRAPHY. Baptista Porta, Magioe Natu- 

 ralis lib. iv., Antverpise, 1560. Fabriciusab Aqua- 

 pendi-nte, De Visione. Venetiis, lu'OO. Aquilonius, 

 Optk-orum, libri iv., Antverpiae, Kil3. Scheiner, 

 Oculus, JSniponti, 1619. De Id Hire, Memoires de 

 Mathematique, ive. Paris, 1694. Gregorius, Optica 

 Promota, sen Kadiorum Mysteria enucleata. Ma- 

 . Script. Optici. B.irroiv, J., Lectiones XVIII. 

 in quibns Opticorum Phenomenon Rationes ex- 

 pommtur. Ma.scres, Script. Optici. Berkeley, A New 

 Theory of Vision, Dublin, 1709. Mariotte, CEuvres, 

 Leide, 1717. Peinberton, De Facilitate Oculi. Haller t 

 Disp. Anat. vol. vii. 1719. Jurin, An Essay on 

 Distinct and Indistinct Vision, Smith's Com pleat 

 System of Opticks, vol. ii. 1738. Porterficld, W M.D., 

 A Treatise on the Eye, 8vo., Edin., 1759. Fontana, 

 Dei Moti dell'Iride, Lucca, 1765. Priestley, J., The 

 History and Present State of Discoveries relating to 

 Vision, Light, and Colours, quarto, London, 1772. 

 Harris, A Treatise of Optics. London, 1775. Otters, 

 De Internis Ocnli Mutationibus, Gott. 1780. Blu- 

 mnibuch, De Oculis Leucaethiopum et Iridis Motu, 

 17xi.;. Maskdyne, Phil. Trans. 179. Hossach, Phil. 

 Trans. 1794. Kamsflen, Phil. Trans. 1795. Du 

 r l\mr, Mem. de Mathematique et de Physique, 

 t. iii. and iv. Dalian J., Extraordinary Facts re- 

 lating to the Vision of Colours. Memoirs of the 

 Literary and Philosophical Society of Manchester, 

 vol. v. pt. i. 1798. Chenevix, Phil. Trans. 1803. 

 Young, 1\, Lectures on Natural Philosophy, London, 

 1x17, and in Philosophical Transactions. Gerson, 

 De Forma Cornea?, Gott. 1810. Horn, On the Seat 

 of Vision, 1813. Wells, Essay on Single Vision 

 with Two Eyes, London, 1818. Chossat, Annales de 

 Cliimie, Paris, 1819. Gillies, J., Account of a Pecu- 

 liar Modification of Vision, Edin. Phil. Journal, 

 vol. ii. 1820. Home, Sir E., Phil. Trans. 1822. 

 Mnxeres, F., Scriptores Optici, London, 1823. Des- 

 s, CEuvres, Paris, 1824-26. Kitchener, Jr., The 

 (Economy of the Eye, 1824. Simonoff, Majendie, 

 Journal dc Physiologic, torn, iv., Paris, 1824 Mile, 

 Journ. de Physiol., torn. vi. Ckantilly, G. de, The'orie 

 des Couleurs et de la Vision, 80. Coddington, An 

 Elementary Treatise on Optics, Camb. 1825. ' Pouiilet, 

 Elemens de Physique, Paris, 1829 Biewster, Sir D., 

 A Treatise on Optics, London, 1831, also in Trans, of 

 Royal Society of Edinburgh, in Philosophical Ma- 



gazine, and in Kdinb. Philos. .Journal. Berlin,!,!, 

 I ber das Aufrecht-erecheinen <ler Ce 



-o..Te 



Tourtval, Die Chromasie des Anges, Al.-< k. 

 Arch. l,s::i. /{,,s ltlt , Handbuch di-r Theoretischen 

 und Practischen Augenheilkunde, Wien, ls:;o. 

 Lloyd, On Light and Vision, Lond., 1881. 

 J,in-/itnmns, De Mutationi- Axis Oculi secundinu 

 diyeraaxo Dtetantiam oi>j(rti, Traj. ad i;ii. i *:;_>. 

 BarteU, Beitrage /.ur Physiologic des Gesichts- 

 Sinnes, Berlin, 1834. FbZtmann, lieitriige zur Phv 



^iiysioiogie i es uesients-Mnnes, Leipz. 1826. ^ 

 Trans. Royal Society of Edinburgh, vol. xiii. >. 

 Treviranus, Beitrage zur Aufklarung der Erschein 

 u. Gesetze des Organised. Lebens. Heft 1. 3. and 

 Beitrage zur Anat. u. Physiol, der Sinneswerkzeuge, 

 1828. Webster, T., Elements of Physics, London, 

 1837. Wernenck, Zeitschrift fiir die Ophthalmologie, 

 Heid., 1837. Seebeck, Ueber den bei manchen Pep- 

 sonen vorkpmmenden Mangel an Farbensinn. Po"-g 

 Ann. 1837. Griffin, D., Lond. Med. Gazette, v.'.i. 

 xxii. 1838. Purkinje, Ainmon's Monatschrift fur 

 Medicin, also Beobachtungen und Versuche zur 

 Physiologic der Sinne, i. Prag., 1823. ; ii. Berl., 1825. 

 Huecli, Die l j .ewegungen der Kiystallinse, Dorp., 

 1839. Herschel, Sir J. W., article " Light," Cyclo- 



V * v t5 T A v -*-' JI J 'dO.UU. U. V/VrCUiOiXUUCy IUUI 4 JJI. 



1840. Mackenzie, W., M.D., The Physiology of 

 Vision, London. 1841. Chevalier, C., Manuel des 

 Myopes, et des Presbyopes, Paris, 1841. Eurlc, 

 Pliny, M.D., On the Inability to distinguish Colours, 

 Amer. Journal of Med. Science, vol. xxxv. Peschel, 

 Elements of Physics, Lond. 1845. Matteuci, Lec- 

 tures on the Physical Phenomena of Living Beings, 

 byJ.Pereira, 1847. Muller.J., Principles of Physics 

 and Meteorology, Lond., 1847. Todd and Bowman, 

 The Physiological Anatomy and Physiology of Man, 

 Lond., 1847. Cooper, W. White, Practical Remarks 

 on Near Sight, Aged Sight, and Impaired Vision, 

 London, 1847. Smee, A., Vision in Health and 

 Disease, London, 1847. Siehel, Lecons Cliniques sur 

 les Lunettes, Brux. 1848. Jones, T. Wharton, The 

 Wisdom and Beneficence of the Almighty, as dis- 

 played in the Sense of Vision, London, 1851. 



(The subject of Vision is more or less treated of in 

 works on Optics and Natural Philosophy; papers 

 on its physiology and pathology are very numerous, 

 and are to be found in Philosophical Transactions 

 and Journals, in the Annales d'Oculistique, &c.) 

 (W. White Cooper.) 



VITAL STATISTICS. The duration of 

 human life, with a consideration of the princi- 

 pal causes by which it may be lengthened or 

 curtailed, is a subject which evidently belongs 

 both to the domain of physiology and to that 

 of statistics. It belongs to phvsioloiry, in- 

 asmuch as the duration of human life is the 

 final effect of the operation of natural causes 

 brought to bear on the healthy human frame ; 

 and it belongs to statistics, whether we use 

 that term in the less exact sense of a branch 

 of human knowledge largely indebted to the 

 use of numbers, or in the more accurate sense 

 of a department of science, having an ii.i- 

 portant bearing on the interests of the public.* 



In this place it is proposed to take only 

 a limited view of the subject of Vital Sta- 

 tistics, and to examine the scientific methods 

 \\hich have been suggested and employed for 

 determining the true duration of human life in 

 communities and classes of men ; in other 



* For some remarks on the true meaning of the 

 term "Statistics," see STATISTICS, MEDICAL, note 

 p. 803. 



