45° 



DISCOVERY REPORTS 



Foetuses 



A series of measurements similar to those taken upon adult kidneys has also been 

 collected for foetal kidneys. The figures are given in Tables III and IV. These figures 

 are not averages but single measurements and include kidneys from both sides of the 

 body, so that the right and left organs can be compared. All three dimensions are 

 seen to increase rapidly with the length of the foetus. On the whole, among male 

 Fin foetuses, the left kidney is shorter than the right by an amount varying from 1-5 to 

 2-5 cm. The average difference for the thirteen foetuses in which both kidneys were 

 measured is 1-5 cm. Among female Fin foetuses this difference is not so apparent. 

 Among Blue whales (Table IV) the difference is apparent in the two female foetuses 

 whose kidneys were measured, but among male Blue whales no figures for the right 

 kidney have been obtained. There appears to be no constant difference between the 

 breadth or depth of the kidneys of the two sides of the body. 



The ratios length-breadth-depth and length-breadth are shown for foetal kidneys in 

 Tables III A and IV a. 



The chief point brought out by these figures is the greater comparative breadth and 

 depth than in the adult. The length of the right kidney of male Fin whale foetuses is six 

 times the depth and two and a half times the breadth, and the breadth is only two and 

 a quarter times the depth. On the left side the length of the organ is only about five 

 and a half times the depth and two and a quarter times the breadth. Similar differences 

 between the ratios for the adult and foetus are observable in the female sex (Fin whales). 

 In Blue whales the increased depth of the foetal kidney is even more noticeable (except 

 in the only two male foetuses examined). 



The foetal ratios may be stated roughly as follows : 



Fin males 

 „ females 



Blue males 

 ,, females 



Right 



Length 

 5i 



Breadth 



A 



A 



Depth 

 1 

 1 



Length : Breadth 

 2l : 1 



2i 



In Fig. 36 the foetal kidney numbers (obtained in the same way as in the adult and 

 comparable with them) are plotted against the body length of the foetus. The growth 

 curve of the kidney is now seen to be of the usual shape, showing a gentle slope at 

 first and becoming gradually steeper. Great acceleration of growth takes place in 

 foetuses between i-o and 3-0 m. in length. If Figs. 35 and 36 could have been plotted 

 on the same scale the lines would have been continuous with one another, but owing 

 to the rapid increase with the body length of the kidney measurements in the foetus 

 and to their much slower increase in the adult, the curve would have undergone 

 considerable flattening in its upper or adult part. 



