BRANCH CHORD AT A: CLASS MAMMALIA 



37' 



muscular sac, the bladder. The bladder opens to the 

 exterior of the body by means of a short tube, the 

 tiretJira. Cut open a kidney longitudinally and examine 

 the cut surfaces. 



The two egg-glands of the female mouse lie in the 

 median portion of the abdominal cavity, somewhat below 

 the kidneys, and from the vicinity of each runs an egg- 

 tube. These tubes meet below the bladder, and open to 

 the exterior of the body through the aperture noted below 

 the anus. In the posterior parts of these tubes lie until 

 birth the developing embryos. 



TECHNICAL NOTE. Fora study of the nervous system place the 

 specimen ventral side down and cut through the skull with the bone- 

 cutters or heavy scissors, exposing the brain and spinal cord. 



Note the large bruin (fig. 149), composed of small optic 

 lobes, large cerebrum, cerebellum, and medulla oblongata, 

 followed by the long spinal cord. Note the nerves aris- 

 ing from the brain and spinal cord. 



For a careful dissection of the mammalian nervous 

 system a larger mammal, such as a cat or dog or rabbit, 

 should be used. For guide use a text-book such as, for 

 the dog, Howell's "Dissection of the Dog " ; for the cat, 

 Reighard and Jennings' " Anatomy of the Cat " ; and for 

 the rabbit, Parker's " Zootomy " or Marshall and Hurst's 



Sunfish Toad Snake Sparrow Mouse 



Sp. Cd. 



Fir,. 149. -Diagram of brains of vertebrates; Olf. L., olfactory lobes- Cbr 

 cerebrum ; Md. Br., midbrain (optic lobes) ; CbL, cerebellum ;' Med. 

 Ol>., medulla oblongata ; Sp. Cd., spinal cord. (From specimens.) 



