As regards the first point, the extensive researches of _Andral_ and
_Gavaret_ have shown that in the female sex the quantity of carbonic
acid eliminated by the lungs diminishes when menstruation first appears
at puberty, but increases again at the climacteric age, when
menstruation ceases—whereas in the male a gradual diminution in the
elimination of carbonic acid begins already in the 36th year of life; in
old age the quantity eliminated is greatly reduced in both sexes alike.