METABOLISM 3I5 



This is borne out by the fact that - despite their large mass - Rorquals 

 have a very high kidney-to-body-weight ratio. Unfortunately, other 

 Cetacean kidneys have not yet been studied sufficiently to enable us to 

 come to any definite conclusions on this subject, but it seems reasonable 

 to assume that whales feeding on krill with a salinity equal to that of water 

 will have a larger kidney-to-body-weight ratio than dolphins which feed on 

 fish. In fact, seals wdth the most highly lobulated kidneys feed mainly on 

 crustaceans. Anderson (1878) found that the eight-foot Gangetic Dolphin 

 which feeds on fresh-water fish and other fresh-water animals with a 

 correspondingly low salt content, had kidneys measuring four inches by 

 three inches, with only about eighty lobules each, while the smaller (five 

 feet) porpoise had kidneys measuring six inches by two inches with 250 

 lobules each. Unfortunately, nothing is known of the kidneys of the 

 porpoise's own fresh-water relatives. 



We conclude this chapter with the brief comment that the Cetacean 

 bladder is comparatively small, even though Yazawa established that that 

 of a Fin Whale can hold 5^ gallons of urine. The urine itself is clear and 

 pale, has an acid reaction and contains the normal mammalian proportion 

 of urea. 



