24 THE ANIMALS AND MAN 



to the heart; these are the veins, which empty into a large 

 thin-walled reservoir, the sinus venosus, which in turn con- 

 nects with the right auricle of the heart. Three large veins 

 enter the sinus venosus, namely, two pre-caval veins at the 

 anterior end, and a single post-caval vein at the posterior 

 end. Trace out the larger arteries and veins from the heart 

 to their division into or origin from the smaller vessels. 



Technical Note. — Carefully remove the heart together with the 

 lungs. The lungs may be inflated by blowing into them through the 

 laryngotracheal chamber with a quill and tying them tightly, after 

 which they should be left for several days to dry. When perfectly dry, 

 sections may be cut through them in various places with a sharp knife, 

 and by this means a very good idea of the simple lung structure of the 

 lower backboned animals can be obtained. With a sharp knife cut 

 the heart open, beginning at the tip (ventricle) and cutting up through 

 the conus arteriosus and the two auricles. Note the valves in the 

 heart which separate the different compartments. 



Note on either side of the median line in the dorsal region 

 a pair of reddish glandular bodies, the kidneys. Attached 

 to the kidneys of the male are two white ovoid glandular 

 masses. These are the reproductive organs. From each 

 kidney trace a tube, ureter, posteriorly toward the region 

 of the anus. The kidneys are the principal excretory organs 

 of the body. The blood which flows through the delicate 

 blood-vessels in the kidney gives up there much of its waste 

 products. These pass out through small tubules of the 

 kidneys into the ureters, which carry the wastes toward the 

 anus. Along one side of each kidney may be seen a 

 yellowish glistening mass, the adrenal body. 



In some of the specimens studied, the body cavity may be 

 filled with thousands of little black spherical bodies. These 

 are undeveloped eggs lying in the female reproductive or- 

 gans situated on each side of the post caval vein. They are 

 deposited by the mother toad in the water in long strings 

 of transparent jelly, which are usually wound around sticks 

 or plant-stems at the bottom of the pond -near the- shore. 



