Muscular Anatomy of the Marsupials, 129 



above it, so as to form an acute angle^ and is liable to be stretched 

 by every depression of that bone. 



The marsupial bone, as is well known, turns upon a long 

 hinge coinciding nearly with the pectineal line of the ilium, and 

 is raised and depressed by the following muscles, which tend to 

 turn it round that hinge ; — 



1. Levators of the Marsupial Bones. 



1. The external oblique takes its origin from the lumbar 

 fascia and from all the ribs except the first, and is inserted into 

 the whole length of the marsupial bone, as well as into the inner 

 edge of the pubes and edge of the ilium. This muscle is con- 

 tinuous with the pectoral at the extremity of the sternum, and 

 weighs in the Giant Kangaroo 5-35 oz. Its exerts little, if any, 

 action on the marsupial bone in its usual position in the wall of 

 the abdomen ; but when this bone is depressed by the weight of 

 the young in the marsupium, the external oblique is capable of 

 acting as a powerful levator ossis marsupii. 



2. The rectus abdominis takes its origin from the first rib 

 and middle line of the sternum and abdomen, and is inserted 

 into the anterior surface and inner edge of the marsupial bone 

 only, of which it is the proper levator. In the Giant Kangaroo 

 it measures 27 inches in length, and weighs 3*43 oz. 



2. Depressors of the Marsupial Bones. 



1. The pectineus takes its origin from the pectineal line and 

 base of the marsupial bone behind the spine of the pubes, and 

 acts as one of the depressors. It is inserted into the second 

 fourth of the linea aspera. It weighs in 



The Giant Kangaroo 0*36 oz. 



The Wallaby 0*25 „ 



2. The adductor brevis takes its origin from the anterior line 

 of the pubes, inside the adductor magnus, and is inserted into 

 the upper fourth of the linea aspera. It acts as a depressor of 

 the marsupial bone, and weighs m 



The Giant Kangaroo 0*25 oz. 



The Wallaby 0*21 „ 



3. The adductor magnus takes origin from the anterior edge 

 of the pubes, from the base of the marsupial bone, from the 

 symphysis pubis, and from the top of the pubic arch, and is 

 inserted into the whole length of the linea aspera. It is a 

 depressor ossis marsupii, and weighs in 



The Giant Kangaroo 5'22 oz. 



The Wallaby 2-9(3 „ 



