THE ENGLISH SPARROW. 225 



closely they are fitted into the dorsal part of the body 

 cavity, and how deeply they are indented by the ribs. 



VI. Renal and Reproductive Organs. There yet re- 

 main in the posterior dorsal part of the body cavity the 

 brownish, trilobed kidneys, partly hidden by the repro- 

 ductive organs, a pair of roundish or oval, light-colored 

 testes, in the male ; a single, larger ovary, often showing 

 developing eggs, in the female. All these organs com- 

 municate by separate ducts with the cloaca. Remove 

 the kidneys, noting their relations to the pelvic bones 

 and to the sacral spinal nerves. 



Concluding Work. Find two regions in the spinal 

 column in which the vertebrae are wider than in other 

 parts. Observe that the spinal nerves issuing in these 

 regions are larger than the others. To what parts are 

 these spinal nerves distributed? 



Cut the skin around the base of one of the legs, and 

 pull it off like a stocking wrong side out. Dissect apart 

 the muscles to find the mechanism by means of which the 

 toes are clasped automatically when the bird sits perch- 

 ing. Of what advantage is this to the bird ? 



Loosen the bird, turn it over, and pull the skin entirely 

 off from the head. The pockets in the skin, which are 

 fitted down into external auditory openings, may readily 

 be pulled out, but the attachment at the eyes will have to 

 be cut. Then carefully cut away the top of the cranium, 

 and the membranes that lie beneath it, closely covering 

 the brain. Having fully exposed the brain, carefully 

 lift it out, beginning at the anterior end, and severing 

 the cranial nerves as soon as they are exposed. Place the 

 brain at once in alcohol to harden for future study. 



Study of the Circulatory System. In an injected 

 specimen 1 study the circulatory organs. The heart has 



1 For method of injection see Appendix, p. 286. 



NEED. ZOOL. 15 



