PARTS AND FEATURES 



also the case in some terrestrial species with octodont affinity. The coypu 

 and capybara are said frequently to swim about with the young perched 

 on the back, and apparently the latter are able to nurse from this position. 



Sirenians are reported to nurse while the parent maintains an upright 

 posture with the young clasped by the flippers, although I do not see 

 how the latter could reach the nipple from this position. 



There are numerous reports on the mammary equipment of the Ceta- 

 cea. The gland itself is apparently of the usual histological character but 

 there are numerous and rather large galactophorous sinuses which open 

 into a lacteal duct or reservoir of generous proportions. Engle (19'27) 

 found that in a female humpback 44 feet long the mammary glands, in 

 full function, had a length of about 6 feet and the greatest diameter of 

 18 inches. The lacteal capacity of a large whale must surely be aston- 

 ishing and a great many gallons. The nipple is retracted within a slit- 

 like orifice on either side of the genito-excretory labia. 



There is a great deal of uncertainty regarding the way in which the 

 cetacean mammillae are employed. The great storage capacity should 

 indicate that the milk is removed at a rapid rate. The presence super- 

 ficially of a part (at times disconnected from the main sheet) of the 

 panniculus carnosus muscle makes it not unlikely that this may assist 

 in the voluntary and forcible ejection of the fluid. And the situation 

 of the nipples introduces a further element of uncertainty. I have been 

 told of a female finback in full milk whose nipples protruded to the 

 extent of one foot when she was inflated with air, and there are a very 

 few published accounts of protruding nipples. The condition is so sel- 

 dom encountered, however, that I regard it as doubtful whether it ever 

 occurs after death save in the event that an animal in full milk has been 

 inflated to usual degree by introduced air or by gases of decomposition, 

 and possibly the sudden death of the calf and. consequent engorgement 

 of the mammary glands might have the same effect. On the other 

 hand the securing under water of milk by the young would be so diffi- 

 cult without temporary protrusion of the nipple that I regard it as 

 highly probable that this takes place, and this could easily be accom- 

 plished when necessary by contraction of the mammillary smooth muscle. 



There has been much speculation regarding the cetacean position for 

 nursing. Obviously if the dam rolls over on her side so that the blow- 

 hole of the nursing young is above the surface the female's blow-hole 

 is submerged. If hers is elevated "then the young is completely below 

 the surface; but Scammon (1874) illustrated the act in this position. 

 Perhaps either posture is employed. 



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