120 THE ENGLISH SPARROW. 



important part in respiration, acting together with the pneumatic 

 cavities of the bones, as chambers for residual air. The entire 

 lung space is, therefore, free to receive fresh or tidal air at each 

 inspiration. 



Technical Note. With a moderately stout pair of scissors -finish the cut 

 around the edges of the breastbone, severing the ribs, the coracoid 

 bones, and the furcula. Carefully lift and remove the whole structure. 

 Also cut away the remainder of the ventral abdominal covering. 



Note the following: 



a) The heart surrounded by a thin pericardium which was probably 



torn in dissection. Distinguish the main systemic veins entering 

 the right auricle and the light colored aorta, with its large 

 branches, given off from the left ventricle. From the right 

 ventricle run two short pulmonary arteries, and the left 

 auricle is entered by two pulmonary veins. 



b) Behind the heart is the reddish-brown liver. How many lobes has 



it ? Look for a gall bladder and for ducts leading from the liver. 



c) On the left side of the body, beneath the liver, is the gizzard, a hard 



muscular structure for grinding the food. 



d) A short, mottled portion of the food tube just preceding the gizzard 



and differing in structure from the remainder of the tube, is called 

 the proventriculus. 



e) Following the gizzard is a long loop of the alimentary canal termed 



the duodenum. Within this loop note a pinkish gland, the 

 pancreas. Find, if possible, the ducts by which the pancreas 

 opens into the duodenum. 



f) Trace the intestine from the duodenum to its termination in the 



cloaca. Note, a short distance from the end, a pair of blind 

 pouches, the coeca. 



g) Look for the spleen, a small ovoid red body attached to the proven- 



triculus. 



h) Snip off the alimentary canal near each end and lay it aside for 

 further study. Observe, in the region beneath the heart, the 

 pinkish lungs, their dorsal surfaces fitting closely into the spaces 



