72 ■■-■-, Mr. Morgan's Description 



of the marsupial bones towards each other ; and being situated 

 immediately behind the mammae, they are altogether prevented 

 by that circumstance from affording the slightest support to 

 the mamma itself. 



The marsupial bones thus confined in their situation by liga- 

 ments, and by the surrounding muscles in which they lie imbed- 

 ded, afford from their situation a firm inferior support to the 

 abdominal viscera, and form an unyielding partition between 

 those parts and the pouch. But another important purpose 

 seems to be answered by these structures. I have already de- 

 scribed two muscles, which are formed for the purpose of com- 

 pressing the mammary gland ; and I have mentioned also the 

 continuity of these two muscles by the interlacement of their 

 fibres over the linea alba {tab. 5. f. a.). These muscles form 

 from their situation a sort of girdle around the belly immediately 

 above the pelvis, and would necessarily, when put into action, 

 press the mammary glands against the comparatively yielding 

 sheet of abdominal muscles which lies behind them, were it not 

 for the marsupial bones, which prevent any compression of the 

 lower part of the abdomen from the action of the mammary 

 muscle, and at the same time receive the glands themselves 

 upon their concave anterior edges. These edges afford a hard 

 and solid point of resistance, against which the glands are 

 pressed ; and their secretions are thus forced through their ex- 

 cretory ducts towards the teats. 



It appears to me probable, that in the Kangaroo, the loose 

 connection of the mammary gland to the subjacent textures 

 may allow of its being drawn backwards and forwards across the 

 edge of the marsupial bone, by the alternate contraction and 

 relaxation of its proper muscle, and thus the process of emptying 

 its ducts by pressure may be considerably facilitated. 



That Nature in other cases avails herself of the agency of 



muscular 



