254 



SHINKISHI HATAI 



Chart 1 Showing the weight of the thymus of the albino rat according to age. 

 The observed weights are represented by 229 males (165 Jackson and 64 Wistar) 

 and 207 females (179 Jackson and 28 Wistar). 

 •Male 



"-^Female 



observed weight 



computed weight 



Similarly, we find the body weight of the ordinary female rat 

 at 85 days of age to be about 132 grams (Donaldson '06). The 

 corresponding weight of the ovaries is 0.045 grams (Hatai '13). 

 The body weight of 350 grams may be taken as that of the fully 

 grown female rat, and we obtain 0.052 grams as the corresponding 

 weight of the ovaries. From these relations we find that nearly 

 87 per cent of the final weight has been attained by the ovaries 

 when the rat is 85 days old. 



The relations indicated above are of interest in connection with 

 the close physiological association between the sex glands and 

 the thymus, as pointed out by a number of investigators (for 

 literature see Biedl '13; Paton '13; and Vincent '12). 



From the chart the considerable variability in the weight of 

 the thymus is clearly seen, a variability the significance of which 

 is increased when we consider the large number of cases which 



