356 MR. J. BESWICK 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 alartendon. Again, the biceps 
portion (Pl. 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 eyidently 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 metacarpal. 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 parallel to each other, and are connected in the middle of their 
course by an intercommunicating tendon, about aninchlong. Both tendons are attached by their distal extre- 
mities to the tendon of origin of the fusiform extensor carpi radialis 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 with that of the extensor carpi radialis longior, 
In the Heron (Ardea cinerea) and Cormorant (Phalacrocorax carbo) only a part of the middle one of the three 
tendons joins the extensor carpi radialis longior. Very frequently this excentric muscle is still 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 Duck, Wood-pigeon, Ptarmigan, Cormorant, Red- 
throated Diver, Lapwing, Snipe (Scolopax gallinago), 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. 
