2ÖÖ WHALES 



even the most superficial glance will reveal a striking resemblance 

 between Cetaceans on the one hand and Ruminants (camels, cattle, deer, 

 sheep, etc.) and some leaf-eating apes (e.g. the guereza) on the other 

 (Fig. 1 68). The reader may have learnt at school that a cow has a complex 

 forestomach consisting of paunch (rumen), honeycomb bag (reticulum), 

 and manyplies (psalterium). All these compartments are covered with 

 cornified epithelium and have no glands. They can therefore be com- 

 pared with the Cetacean forestomach, and are, in fact, anatomically 

 identical with it, but they differ in their physiological function. Thus, the 

 intestinal glands of cattle do not produce enzymes for breaking down the 

 cellulose on which these animals chiefly feed, nor, for that matter, are such 

 enzymes secreted by the glands of any vertebrates. The break-down is 

 therefore effected by the enzymes of millions of unicellular animals and 

 plants which live in the paunch of cattle. No traces of them have ever 

 been found in those of Cetaceans, which must therefore break down 

 their food in a different way. 



The secret of the digestion of whales and dolphins must be sought in the 

 highly muscular wall of the forestomach (which in Fin Whales can be up 

 to three inches thick) , in the tough lining and the presence of marked 

 pleats in this wall, and finally in the piesence of sand and small stones 

 which, at least in some species, are too common to be accidental and must 

 therefore play some part in digestion. Van Beneden, for instance, while 

 investigating the stomach of a Pilot Whale in i860, discovered a number 

 of pebbles in the first compartment, the biggest weighing i ounce, and 

 Malm (1938), while investigating another Pilot Whale, found stones 

 weighing altogether twenty-one pounds. It would therefore appear that, 

 like the muscular stomach of birds, the first Cetacean stomach compart- 

 ment by contracting forcefully can, with the help of stones and sand, 

 break down the food to suitable dimensions. Cetaceans, like birds, swallow 

 their food whole, so that it must be broken down in the first compartment 

 before passing through the very narrow passage to the second. Moreover, 

 the passage often protrudes like a small snout into the first compartment, 

 thus impeding the passage of large particles even farther. The reason why 

 sand and stones are not found in all Cetacean stomachs may well be that 

 the vertebrae offish and the chitin armour of crustaceans provide adequate 

 grinding material. In either case, whales 'chew' their food with their 

 stomachs, just as birds do. This is borne out also by the fact that the first 

 stomach division is relatively small in suckling Cetacean calves which have 

 no need to chew their food at all. In adult Odontocetes, the first compart- 

 ment is by far the largest, but in Mysticetes, which feed on small plankton, 

 the second compartment is bigger than the first. 



Clearly, animals which feed exclusively on food as soft as cuttlefish 



