40 C. M. JACKSON 



b. Ovaries The growth of the ovaries is quite complex. In the 

 relative (percentage) growth curve (fig. 7 b) constructed from 

 data according to Hatai's formulas, two distinct phases are notice- 

 able. In the first phase, beginning at birth, the ovaries increase 

 in relative size from about 0.017 per cent to a maximum of about 

 0.030 per cent at a body weight of 10 to 15 grams. Thereafter 

 the ovaries decrease to about 0.015 per cent of the body weight 

 at 60 grams. Then begins the second period of acceleration, 

 corresponding to the advent of puberty, during which the ovaries 

 increase to a second maximum of about 0.037 per cent of the 

 body weight at 110 to 120 grams. Thereafter the ovaries lag 

 behind steadily in relative growth, and form only about 0.017 

 per cent of the body weight at 300 grams. 



When grouped according to age periods, my data (table 15, 

 fig. 7 b), show considerable irregularity in the relative size of 

 the ovaries. From an average of about 0.017 per cent of the 

 body at birth they increase (after an apparent drop at seven 

 days) to a first maximum of about 0.022 per cent at twenty 

 days. Then they decrease to about 0.020 per cent at six weeks, 

 increasing to a second maximum of 0.034 per cent at ten weeks, 

 the age of puberty. Thereafter they decrease, averaging 0.025 

 per cent of the body weight at one year. 



The extremes recorded in the size of the ovaries (table 15) 

 show a remarkable range. This is due partly to difficulty during 

 the earlier stages in dissecting out the ovaries accurately, and 

 partly to fluctuations in size in the later stages, probably on 

 account of cycles of ovulation. Coefficients of variation were 

 not calculated for the earliest stages, as the data were consid- 

 ered inadequate. For periods from twenty days onward, the high- 

 est coefficient of variation in absolute weight, 50.9, was found at 

 ten weeks (the age of puberty), and the lowest, 32.7, at five 

 months. The coeflScients of variation in percentage weight are 

 somewhat lower (25 to 39); and the coefficient of correlation 

 between ovaries and body weight varies from 0.64 to 0.82 (some- 

 what too high, due to 'spurious correlation'). 



