454 



DISCOVERY REPORTS 



DIAMETER OF THE RENCULI 



The average diamter of the renculi of the kidney was measured in a great number of 

 Fin whales of both sexes and some Blue whales. 



Slices of the kidney substance were cut thick enough to avoid any danger of cutting 

 two sections through the same renculus, and the diameter in cm. was measured of 

 up to forty renculi cut as nearly as possible through the centre of the papilla. Again, 

 in order to avoid any danger of measuring the same renculus twice, only the renculi on 

 one surface of each slice of kidney substance were measured. The average of these 

 counts was taken as the average diameter of the renculi of the kidney. 



The following numbers of such counts were made on the kidneys : 



Great variability, similar to that which characterizes the dimensions of the kidney 

 itself, was found in the diameter of the renculi, and there is no correlation between the 

 size of the renculi and the length of the body. The size of the kidney is the controlling 

 factor in the growth of its component renculi as, indeed, might be expected. The 

 average diameter of the renculi for kidneys represented by a series of kidney numbers is 

 shown in Tables VII A (Fin whales) and VII b (Blue whales). The numbers in question 

 differ by five units and the kidney dimensions (length, breadth and depth) to which 

 these numbers correspond are also shown in the table. (The dimensions represent the 

 average size of the kidney for each range of kidney numbers.) The range of body length 

 to which these kidney sizes and numbers correspond is shown in column 3 of each 

 table. 



Again there is no sex difference between the diameters of the renculi in either Blue 

 or Fin whales, neither does there appear to be any difference in the rencular diameter in 

 kidneys of the same size in the two separate species. 



Fig. 38 represents the curve which results when the rencular diameters (Fin whales 

 only) are plotted against the kidney numbers. It will be noticed that there is a con- 

 siderable drop in the curve opposite kidney numbers from 30 to 40. This seems to be 

 due, not to the fact that the larger kidneys have smaller renculi, but that the largest 

 kidney numbers do not represent the true size of the kidney, for the reason already 

 stated, namely, that an excessive depth but a small length or breadth will produce an 

 unduly large kidney number. The part of the curve, therefore, corresponding to kidney 

 numbers between 30 and 40 has been dotted in Fig. 38. 



The figure demonstrates clearly the absence of any sex difference in the diameters 

 of the renculi. 



