THE ANATOMY OF BIRDS. — ANGEIOLOGY. 
195 
connecting with the flexor digitorum perforatus, — one of the muscles which bend the toes col- 
lectively. When this arrangement obtains, the result is that when a bird goes to roost, and 
squats on its perch, the toes automatically clasp the perch by the strain upon the ambiens that 
ensues as soon as the leg is bent upon the thigh, and the tarsus upon the leg, the weight of the 
bird thus holding it fast upon its perch. The effect is as if an elastic cord were tied to the hip 
joint, thence directed over the front of the knee and back of the heel and so on to the ends of the 
toes. Obviously, such a cord would be strained when the limb is bent, relaxed when the limb is 
straightened out. The reader may observe a corresponding effect of the muscular arrangement 
of his forearm by throwing the hand as far back as possible ; the fingers tend to close by the 
strain on the flexors in passing over what is a convexity of the wrist when the hand is in that 
position. Passeres have no ambiens, the perfection of their feet in other respects answering all 
purposes. Birds having it are termed Jiomalogonatous or ''normally-kneed" (Gr. 6/xaXdy, homalos, 
from o/ioy, homos, like, even, etc.; yow, yovaros, gonu, gonatos, knee) j those wanting it are called 
miomalogonatous, " abnormally-kneed." The distinction prevails with much applicability to 
various large groups of birds, and does good duty in diagnosis when duly connected,with other 
characters; but surely should not give name to primary groups founded upon it! Other 
muscles of the leg much used by the same sagacious and zealous anatomist are the femoro- 
caudal, accessory femoro-caudal, semitendinosus, and accessory semitendinosus. The whole five 
of these muscles ' ' vary ; any one or more than one may be absent in different birds ; . . . the con- 
stancy of the peculiarities in the different individuals of each species, or the species of each 
genus, and very generally in the genera of each family, makes it evident to any one working at 
the subject that much respecting the affinities of the different families of birds is to be learnt 
from the study of their myology, in connection with the peculiarities of their other soft parts ; 
and that these features will, in the long run, lead to a more correct classification than one based 
on the skeleton alone, becomes almost equally certain." (Garrod, P. Z. S., 1873, p. 630.) I 
quote in justice of this author, a modem Macgillivray in sincerity and love of truth ; and very 
generally, in constructing my characters of the higher groups of birds in the body of this work, 
I shall be as glad to use the myological formulae of Garrod, as I am here to pay this slight 
tribute to his memory. 
d. Angeiology: the Vascular or Circulatory Systems. 
Blood and Lymph are the two media by the circulation of which throughout the body 
the various amojboid animals which compose the tissues are fed, their waste repaired, and their 
dead parts removed. Each species of Amoeba has the faculty of selecting from the constituents 
of blood and lymph its appropriate food; and of converting such nourishment into its own 
proper substance. Refuse matters are either drained off by the kidneys and voided as excrement, 
or swept by the current of blood into the lungs and there cremated. The stream of lymph is a 
feeder to the blood, and when the mingled currents are no longer distinguishable has become 
blood. The machinery of circulation is two sets of vessels — the Jicematic, or vascular system 
proper, consisting of the heart, arteries, veins and capillaries for the blood-circulation ; and the 
lymphatic, consisting of lymph-hearts and vessels, for the flow of lymph. The lymphatics, 
converging fi-om all parts of the body, and especially from the intestines, end in vessels which 
pour the lymph into the veins of the neck. The heart is the central organ of the blood-circu- 
lation, by which that fluid is pumped into all parts of the body through the arteries or efferent 
vessels ; straining through the network of capillaries, it returns to the heart through the veins, 
or afferent vessels. The set of efferent vessels is the arterial system ; that of afferent vessels is 
the venous system. The blood in arteries excepting the pulmonary is bright red ; that in 
veins excepting the pulmonary is dark red. The change from bright to dark occurs in the 
capillaries of the system at large ; the change from dark to bright only in the capillaries of the 
lungs and air-sacs. The systemic blood circulation is completely separated from the pulmonic 
