Chap, hi.] THE PHASES OF LIFE. 1151 



The baby boy is heavier and taller than the baby girl, and the 

 maiden of five breathes Avith her ribs in the same way as does 

 the matron of forty. The woman is lighter and shorter than 

 the man, the limits in the case of the former being from 1-441 

 to 1-740 metres of height and from 39-8 to 93-8 kilos of weight, 

 in the latter from 1-467 to 1-890 of height, and from 49-1 to 

 98-5 kilos of weight. The muscular system and skeleton are 

 both absolutely and relatively less in woman, and her brain is 

 lighter and smaller than that of man, being about 1272 grammes 

 to 1424. Her metabolism, as measured by the respiratory and 

 urinary excreta, is also not only absolutely but relatively to 

 the body-weight less, and her blood is not only less in quantity 

 but also of lighter specific gravity and contains a smaller pro- 

 portion of red corpuscles. Her strength is to that of man as 

 about 5 to 9, and the relative length of her step as 1000 to 

 1157. 



§ 718. From birth onward (and indeed from early intra- 

 uterine life) the increment of growth as we have seen, though 

 undergoing certain variations, continues to diminish. At last 

 a point is reached at which the curve cuts the abscissa line, and 

 the increment becomes a decrement. After the culmination of 

 manhood at forty and of womanhood at the climacteric, the 

 prime of life declines into old age. The metabolic activity of 

 the body, which at first was sufficient not only to cover the 

 daily waste but to add new material, later on is able only to 

 meet the daily wants, and at last is too imperfect even to sus- 

 tain in its entirety the existing frame. Neither as regards 

 vigour and functional capacity, nor as regards weight and 

 bulk, do the turning-points of the several tissues and organs 

 coincide either with each other or with that of the body at 

 large. We have already seen that the life of such an organ as 

 the thymus is far shorter than that of its possessor. The eye 

 is in its dioptric prime in childhood, when its media are clearest 

 and its muscular mechanisms most mobile, and then it for the 

 most part serves as a toy ; in later years, when it could be of 

 the greatest service to a still active brain, it has already fallen 

 into a clouded and rigid old age. The skeleton reaches its 

 limit very nearly at the same time as the whole frame reaches 

 its maximum of height, the coalescence of the various epiphyses 

 being pretty well completed by about the twenty-fifth year. 

 Similarly the muscular system in its increase tallies with the 

 weight of the whole body. The brain, in spite of the increas- 

 ing complexity of structure and function to which it continues 

 to attain even in middle life, early reaches its limit of bulk and 

 weight. At about seven years of age it attains what may be 

 considered as its first limit, for though it may increase some- 

 what up to twenty, thirty, or even later years, its progress is 

 much more slow after than before seven. The vascular and 



