BRANCH CHORDATA; CLASS AYES: THE BIRDS 333 



bird there is a complete double circulation. Its blood is 

 not mixed, the pure with the impure, as in the toad and 

 snake. Blood passing through the right auricle and i'cn- 

 triclc goes to the lungs; on its return to the heart purified, 

 it enters the left auricle and left ventricle, thence to pass 

 out over the body through the arteries. 



Note the large corta given off from the left ventricle. 

 Note the two large branches, the innominate arteries, 

 given off by it near its origin. Each innominate divides 

 into three smaller arteries, a carotid, branchial, and pec- 

 toral. The aorta itself turns toward the back and con- 

 tinues posteriorly through the body as the dorsal aorta. 

 To the right auricle come three large veins, the right and 

 left pracavce and the postcava. Each praecava is formed 

 by three veins, faejugvlar from the head, the branchial 

 from the wing, and the pectoral from the pectoral muscles. 

 The postcava comes from the liver. From the right 

 ventricle go the short right and left pulmonary arteries 

 to the lungs, and from the lungs the blood is brought to 

 the left auricle through the right and left pulmonary veins. 



TECHNICAL NOTE. For a detailed study of the circulation of 

 the bird the teacher should inject the blood system of some larger 

 bird, as a pigeon or fowl, for a class-demonstration. (For a guide, 

 use Parker's " Zootomy," p. 209, or Martin and Moale's " How to 

 Dissect a Bird," pp. 135-140 and pp. 148, 149.) 



In the posterior dorsal region of the body-cavity will 

 be found large three-lobed organs fitting into the spaces be- 

 tween the bones of the back on either side. These are the 

 kidneys, and from their outer margins on each side a ureter 

 runs posteriorly into the cloaca. Overlying the anterior 

 ends of the kidneys are the reproductive organs. In the 

 male these glands consist of firm, whitish, glandular 

 bodies. From each runs a long convoluted i>as defcrens, 

 which enters the cloaca. This tube corresponds to the 

 egg-duct of the female. In the female the right egg- 



