Aves. 119 



they are composed of several lobes, which fit into the hollows 

 of the pelvis. After removing the kidneys, observe the white 

 nerves extending outward from the sides of the spinal column to 

 pass to the thighs. 



21. In front of the kidneys are the two white oval spermaries, 

 in the male ; in the female, the ovary, often showing many eggs in 

 different stages of development. The kidneys and reproductive 

 organs send tubes to the cloaca ; the tube which conveys the eggs 

 from the ovary to the cloaca is the oviduct. 



22. Remove the heart, cut off the auricles, and look down 

 into the ventricles ; cut across the middle of the ventricles, and 

 make a drawing of this cross section. 



23. Observe the fold of skin extending across the angle be- 

 tween the arm and forearm ; dissect away the skin, and find a 

 membrane within the skin fold. 



24. Observe the muscles connecting the hinder edge of the 

 breastbone and the pelvis (which were cut through in opening the 

 abdomen) ; these are the abdominal muscles. How does the bird 

 perform the act of breathing ? Compare the bird, snake, frog, 

 and man, in their modes of breathing. 



25. Bend the leg up close to the body, to the position of 

 perching ; what effect does this bending of the leg have on the 

 toes ? How does the bird stay securely on the perch when 

 asleep ? Dissect the leg to find the mechanism by which the 

 toes are clenched as the leg is bent. 



26. Dissect out the tongue, and compare it with the tongue 

 of the snake. 



27. Clean away as much as possible of the soft tissues, and 

 keep the skeleton for later study. 



THE BRAIN OF THE PIGEON. 



. Cut away the top of the skull with a sharp knife, using great care 

 not to injure the soft brain, and make out the following parts : 

 i. In front, the large cerebrum, consisting of two hemispheres, 

 which are separated by a deep groove. 



