456 DISCOVERY REPORTS 



Even discounting this upper part of the line its shape is still that of a gentle curve. In 

 other words, the diameter of the renculi does not increase evenly with the size of the 

 kidney in the adult, but begins to lag behind the growth of the organ when the kidney 

 reaches a size represented by the numbers 20 and 25. This kidney size corresponds to a 

 body length of 21-0 m. for male whales and 21-0-22-0 m. for females. This is about the 

 length at which the growth of the body ceases. It may perhaps be assumed that the 

 shape of the curve is due to the fact that when the body has begun to slow down in 

 growth, the renculi begin, one by one according to their individual conditions of growth, 

 to cease to grow also, but that they do not all cease increasing in diameter at the same 

 time and also still continue to grow apart, so that increase in the size of the whole organ 

 continues to take place, but increase in the average diameter of the renculi falls off. 



In Table VIII the rencular diameters are shown for foetal Fin whales of body lengths 

 from about 1 -o to about 4-0 m. and in Fig. 39 these diameters are shown plotted 

 against the foetal kidney numbers. Each figure shown in the table represents one 

 count often renculi performed upon one kidney and is not representative of a large num- 

 ber of separate counts as are the same figures for the adult. For this reason the points in 

 the upper part of the figure become more and more scattered as the individual renculi 

 begin to show more and more variations in size. The shape of the curve, however, is 

 evident. The renculi increase rapidly in diameter with the increase of the kidney up to 

 sizes represented by the number 0-05. This corresponds to body lengths in the region 

 of 2-0 m. This is the stage at which the renculi become differentiated from the lobules. 

 After this point the line straightens out and the increase in diameter of the renculi 

 may be said to be directly proportional to the size of the kidneys. The foetal and 

 adult graphs may be assumed to be continuous so that this relation between the 

 renculi and the dimensions of the kidney holds throughout the growing period of the 

 whale until growth begins to slow down, when increase in diameter of the renculi ceases 

 gradually before that of the kidney itself. 



NUMBER OF RENCULI IN THE KIDNEY 



One estimation only was made of the numbers of renculi in the kidney. The method 

 used is a rough one and was applied to the kidney of the one female Fin whale whose 

 kidney was weighed. The weight of the kidney was 65-5 kg. 



The number of renculi counted in a given area (20 x 20 cm.) was between 80 and 85. 



The weight of a given block of the kidney substance measuring 20 x 20 x 5 cm. was 

 1-82 kg. 



The average diameter of the renculi (a count of 40) was 2-4 cm. 



The number of renculi in the block was therefore : 



(80 or 85) x £2. 

 2-4 



The above gives the number counted in the given area multiplied by about two, since 

 the block of kidney was about twice (5/2-4) the rencular diameter in depth. 



