THE CIRCULATORY APPARATUS OF BIRDS. 647 



detached separately from the cistern, one follows the right side, the other the left side of 

 the aorta, describing an arch whose concavity is downward at the base of the heart, on 

 the lateral parts of the trachea, terminating either very near one another, and on the same 

 transversal line, at the junction of the two jugulars, or one to the right, the other to the left, 

 in each of these two veins, and not far from their junction with the axillaries (Fig. 307.) 

 " When the two canals arise from the sublumbar reservoir, they sometimes repeatedly 

 anastomose with each other by sinuous and curved branches, as shown in figure 308. 



Fig. 309 



THORACIC DUCT OF SMALL RUMINANTS. 



" Then all the branches collect in the anterior mediastinum, and constitute a single 

 canal which, near its termination, again subdivides into four vessels that open separately, 

 two to the right and two to the left, in the usual place. 



" This variety is the most remarkable and complicated of all those observed in the 

 domesticated animals. 



PIG. " The thoracic duct of the Pig, usually single throughout its whole extent, 

 is sometimes divided, at one to one and a-half inches from its insertion, into two branches 

 which soon reunite in an oval dilatation ; this, after receiving the vessels from the head, 

 neck, and limbs, opens towards the extremity of the left jugular. 



CARNIVORA. " In the Dog, Pecquet's reservoir is enormous ; in shape it is ovoid, 

 and is prolonged between the pillars of the diaphragm into the thoracic cavity. The 

 thoracic duct of this animal generally resembles that of the Pig. Yet it sometimes 

 offers in its course and termination very numerous variations : Rudbecky has noticed a 

 bifurcation above the heart, and another bifurcation whose branches anastomose with 

 each other several times. Swammerdam and Stenon have figured numerous irregular 

 anastomotic divisions towards the middle of a single canal, to its point of departure. These 

 old authors have indicated and represented double and triple insertions of different 

 forms. Lastly, Bilsius has shown an arch, or rather a very remarkable ring, at the 

 entrance of the conduit, and at its junction with the lymphatic vessels of the neck and 

 anterior limbs, and which is more or less analogous to that which I have observed on 

 several occasions in the Horse, Pig, and Cat." 1 



CHAPTER III. 

 THE CIKCULATORY APPARATUS OF BIRDS. 



WE will briefly examine the characteristics of the different portions of the circulatory 

 apparatus the heart, blood-vessels, and lymphatic vessels of birds. 



ARTICLE I. THE HEART. 



The heart, in birds, is situated quite at the entrance to the chest, in the median line, 

 and is contained in a pericardium that adheres to the posterior diaphragmatic septum 



G. Colin, op. cit. 



