AVKS. 247 



by the union of two iliac veins, and running through the liver, 

 from which it receives two hepatic veins, to the heart. 



The iliac on each side commences between the anterior and middle 

 kidney-lobes where the femoral vein, bringing back blood from the greater 

 part of the hind-limb, imites with the hypoi/astric vein to form it. The 

 latter traverses the substance of the kidney, behind which it is connected 

 with its fellow by a cross-branch, that receives the caudal vein from the 

 tail, and internal iliac veins from the pelvis, and is also united with the 

 hinder end of the posterior mexenteric vein. The sciatic vein carries blood 

 from the hinder part of the leg into the hypogastric, at the junction of the 

 middle and posterior kidney-lobes. These lobes return their blood by a 

 large superficial renal vein to the iliac vein, which also receives a small vein 

 from the anterior lobe. 



(-) Hepatic Portal System. This, the only portal system 

 present in the pigeon, is entirely made up of vessels running to 

 the liver from the alimentary canal and spleen. 



Into the left liver-lobe two small left gastric veins take blood from the 

 left side of the gizzard, while the large portal vein divides into two 

 branches, one for each liver-lobe. This vein is formed by the union of 

 three others gastro-duodenal, returning blood from the right side of the 

 gizzard, duodenum, pancreas, and last loop of the small intestine ; anterior 

 mesenteric, from the rest of the small intestine; and posterior mesenteric 

 from the large intestine and cloaca. (The hypogastric veins receive part of 

 their blood from this vessel. ) The spleen pours its blood directly into the 

 portal trunk. 



(3) One or two short pulmonary veins from each lung unite 

 together and open by a single aperture into the left auricle on 

 its dorsal side. 



Circulation. The two sides of the heart do not directly com- 

 municate, and therefore no mixing of blood occurs, as in the 

 frog. The impure blood from the body is poured into the right 

 auricle by the caval veins, and passes into the right ventricle, by 

 which it is forced into the lungs. Thence the oxygenated blood 

 is returned to the left auricle, and, passing into the left ventricle, 

 is pumped through the aorta to the body at large. 



The movements of the heart are very vigorous. The auricles 

 contract together, and their systole is followed by a ventricular 

 systole, both ventricles contracting together. The auriculo- 

 ventricular valves prevent the blood from passing back into the 

 auricles, and the chordae tendinese prevent the valvular flaps from 

 going too far. The chordae would be slackened during the ven- 

 tricular systole by the approach of the ventricular walls, were 

 this not compensated for by the papillary muscles, which con- 



