356 ME, J. BBSWICK PERRIN ON THE 



The description of the extensor longus alaris presents remarkable differences from that 

 commonly met with in birds. I could not detect any trace of the elastic band which 

 is so common a constituent of the central portion of the alar tendon. Again, the biceps 

 portion (PI. LXIV. fig. 3) was isolated from the delto-pectoral portion, and constituted 

 the main distal alar tendon. This arrangement is only one of the many dispositions 

 met with in different birds \ 



The 2nd pectoral is an oblong, bipennate muscle, the angular extremity of the fibres 

 being directed forwards and outwards. It is attached proximally to the lateral aspect 

 and keel of the sternum in entire length, to the sternal extremity of the coracoid, and 



the anterior and shorter arises from the internal tuberosity of the humerus, the posterior and longer from the 

 clavicular extremity of the coracoid bone. In the Ostrich and Rhea, however, both portions arise from the 

 coracoid. The posterior muscle sends down a long thin tendon, which runs parallel with the humerus, and is 

 inserted, generally, by a bifurcate extremity into both radius and ulna. The anterior muscle terminates in a 

 small tendon, which runs along the edge of the aponeurotic expansion of the wing. In this situation it becomes 

 elastic ; it then resumes its ordinary tendinous structure, passes over the end of the radius, and is inserted into 

 the short confluent metacarpal." Professor Owen has evidently in this description combined the biceps flexor 

 with the alar flexor. 



' In the Strix flammea the flexor longus alaris consists of two portions, one derived from the peripheral 

 extremity of the great pectoral, the other from the anterior differentiated portion of the deltoid, as already 

 described. From the common point of union of these two muscles three tendons result, which proceed to their 

 respective insertions enclosed between a duplicate fold of the integuments. The outer tendon occupies the 

 anterior and outer fold of the wing, traverses the base of a triangle, the two sides of which are formed respectively 

 by the humerus and the bones of the forearm in their semiflexed position. It is finally attached by its distal 

 extremity to the base of the rudimentary first metaoai-pal. This tendon is of considerable thickness, owing to 

 the development upon it of a fusiform band of elastic tissue, which, irrespective of muscular action, maintains, 

 in the inactive state, the wing in a flexed position. The two remaining tendons pass down in the interval 

 between the preceding and the biceps, running paraDel to each other, and are connected in the middle of their 

 course by an intercommunicating tendon, about an inch long. Both tendons are attached by their distal extre- 

 mities to the tendon of origin of the fusiform extensor carpi radiaUs longior, one about a quarter of an inch in 

 front of the other. In advance of them there is a second intercommunicating tendon which connects the outer 

 elastic tendon vrith that of the extensor cai-pi radiaUs longior. 



lu the Heron {Ardea cinerea) and Cormorant {Phalacrocorax carlo) only a part of the middle one of the three 

 tendons joins the extensor carpi radialis longior. Very frequently this excentric muscle is stiU further compli- 

 cated by the addition of another tendon, or muscle, which arises either as a segmentation of the biceps, and 

 decidedly continuous with it, or from a fascial expansion springing from that covering and investing the 

 biceps, and invariably from opposite a point corresponding to the lower border of the great pectoral. It usually 

 joins the outermost of the three above-described tendons, although there are several differences from this more 

 general mode of distribution. In the Common Duck, Wild Uuek, "Wood-pigeon, Ptarmigan, Cormorant, Red- 

 throated Diver, Lapwing, Snipe {Scolopa.v rjallinar/o), and many other birds I have noticed this biceps addition 

 to the extensor longus alaris, not always, however, joining it, but sometimes forming a distinct muscle in its 

 entirety. In some specimens, e. g. the Wild Duck, the pectoralis major does not contribute a muscular slip to the 

 extensor longus alaris, the muscle simply consisting of the biceps and deltoid portions, which embrace, prior to 

 their union, the great pectoral insertion. Again, the resulting tendons do not always spring from a common 

 one, but sometimes as three independent tendons from the deltoid portion of the muscle alone. 



