The following is an abbreviation of the English life-table, which will be found given at length for any year of life from birth to 95 years of age in the fifth annual report of the Registrar General.* The table is read thus :—At birth the ex pectation of a male child is 40'19 years, of a female child 4218 years ; at 5 years of age the expectation is 49-64 years for a boy and 50.38 years for a girl ; at 20 years of age, males one with another may expect to live 39'88 years, and females 40'81 years ; at 30 the expectation has fallen to 33'13 for men and 34.25 for women.
4. The mean duration of life, the mean life, the mean life-time, or vie moyenne, is found by adding the age to the expectation of life. Thus the mean duration of life at 5 years of age is for boys, and 5+50.38 for girls, or 54'64 for boys and 55.38 for girls ; at 10 years of age the mean duration of life is, for boys and girls respectively, 10+47.08 and 10+47.81, or 57.08 and and at 30 years of age 30+33.13 or and 30+34'25 or 64'25. The mean duration of life differs from the mean age at death, inasmuch as the one is a calculation based on all the deaths taking place, after a given age, in the members of a community traced through life, while the other is founded upon such deaths as happen to be noted in a community which has been undergoing continual disturbance by births, immigration, and emigration.
5. The probable duration of life, probable life-time, equation of life, or vie probable, is the age at which a number of children born into the world will be reduced one-half, so that the chance is equal of their dying before or after that age. Thus it has been ascertained that out of 51,274 males and 48,726 females (making up together the number of 100,000 infants) at birth, 25,637 males will die between the 45th and 46th year, or at about 451 years of age, and 24,363 females between the 47th and 48th year, or at about 47i. years ; so that the equation of life or probable life-time of males at birth is 45-1 years, and of females 471 years. The same terms (probable life time, equation of life, or vie probable) arc also employed in speaking of persons who have attained more or less advanced ages. Thus the probable duration of life of a female at 25 years of age is about 41 years, being her actual age added to the number of years required to reduce the females living at that age to one half. In like manner the probable duration
of life of a male aged 60 years is 73 years, being his age added to the 13 years required to reduce himself and his contemporaries to one half their number.
The term "specific intensity" has also been used as a measure of the value of life. It represents the number living at any given age, divided by the number dying at that age. For example, if, at the age of 44, 72,709 male survivors of the population of Eng land and Wales, out of 100,000 born into the world, lose by death 990, the specific intensity is ima or 73-475, while for the number of 72,190 female survivors losing 923 of their number, the specific intensity is /Hp, or 78.309. Females, therefore, have a higher intensity of life at 43 years of age than males ; in other words, they stiffer from a less mor tality,* Such are some of the principal methods which have been recommended or employed for ascertaining the true duration of human life,—a branch of statistical inquiry which has received large contributions of late years, many of which, however, arc unfortunately rendered altogether valueless by the omission from the calculations of some elements ne cessary to precision, but not yet obtainable.
VOICE.}—(Syn. Gr. Oman; Lat. Vox ; Fr. Voir ; Germ. Stimme ; It. Voce; Span. Voz.) This term is usually applied to those sounds which animals produce by means of the air traversing their organs of voice, such as we observe in mammal* birds, reptiles, and in some insects.
The human voice is susceptible of several modifications, such as timbre or quality, in tensity, and pitch ; including those successive transitions of tone from one pitch to another which constitute melody. The organs of voice comprise the thorax with the_ muscles of respiration, the lungs, trachea, larynx, pharynx, mouth, tongue, nasal cavities, nerves, and blood-vessels. Of these, the thorax and lungs may be considered an air-chest or bellows, the trachea a porte-vent or air-pipe, and the glottis a complex iee.l. The trachea varies in length and diameter with the age and sex of individuals, until they arrive at the adult period of life. By its structure the trachea is endowed with elasticity, together with the power of longitudinal extension and relaxation, and of increasing or diminishing in diameter : the acoustic effect of these pro perties will presently be investigated.