REPRODUCTION 38 1 



Norwegian whalers. The research was chiefly carried out by E. W. van 

 Lennep and W. L. van Utrecht (who pubhshed a prehminary paper on 

 this subject in 1953) and later by W. A. Smit. Starting from the known fact 

 that, in other mammals, certain histological characteristics of the glandular 

 cells are criteria of lactation and of recent cessation of lactation, the Dutch 

 biologists found that, in the vast majority of cases where milk had gushed 

 from the nipples or had been found in the nipples during dissection, the 

 histological picture, too, showed that the cow had been lactating. In one 

 case, however, lactation was diagnosed histologically, when the carcass 

 had not been 'milk-filled', w^hile, conversely, a few milk-filled carcasses 

 proved, on histological examination, to have stopped their secretory 

 activity. In the first case, the calf had probably just sucked the cow dry, 

 or else the milk had been lost while the carcass was being dragged through 

 the water, and, in the others, some milk must have remained in the ducts 

 even after weaning. Further investigations are proceeding, particularly 

 with a view to establishing some relationship between the histological 

 picture and such macroscopic characteristics as thickness, colour, flexi- 

 bility of the tissue, etc. The final results may well help the inspectors to 

 make their diagnoses with greater accuracy, and, meanwhile, we must 

 take it that using present-day criteria (presence of milk during dissection 

 of the gland, or gushing nipples), their errors cancel out, since they 

 diagnose approximately the same number of false cases of lactation as of 

 false cases of weaning, so that there is unlikely to be any change in the 

 total number of reported breaches. In any case, the number of trans- 

 gressions during recent years has been a mere 0-3 per cent of the total 

 number of animals killed - not a bad figure when we consider the 

 difficulties under which the whaling industry has to work. 



All biologists without exception are agreed that Cetacean calves are 

 always suckled under water, though sometimes so close to the surface 

 that they can be seen (Fig. 215). Sea-cows, sea-otters and hippopotami 

 also suckle their young under the surface, though hippopotami can feed 

 their young on land as well. Seals, sea-lions, and the Pigmy Hippopota- 

 mus on the other hand, invariably suckle their young on land. In the lat- 

 ter, as in all terrestrial mammals, the young pump the milk from the nipple 

 by means of a sucking reflex (cf a milking machine), or else the milk 

 is gently squeezed out of the nipple by a massaging action of the lips 

 (cf. milking a cow or goat by hand). However, neither method is appli- 

 cable under water, and Cetaceans and hippopotami therefore have to 

 squirt their milk into the calf's mouth. 



While suckling their young, Cetaceans move very slowly; the calf 

 follows behind and appioaches the nipple from the back (Fig. 216). The 

 cow then turns a little to the side, so that the calf has easier access to the 



