posting bird laws in conspicuous places, and most important of all, systematic bird work in public schools. The importance of engaging the interest of our youth in birds cannot be overestimated. It results in a double benefit, for the birds will be held in higher esteem and the children will become possessed of a source of lasting pleasure. The nestrobbing, bird-shooting boy and the feather-wearing girl may be made the friends and allies of the birds."-WEED and DEARBORN, "Birds

in their Relations to Man."

But not only should the boy cease to destroy nests and shoot birds; not only should the girl cease to wear any part of a wild bird; but boys and girls alike should do

all they can to induce

others to do likewise. FIG. 77.-Bird house made by a twelveMuch may also be done,

likewise, even in the vicinity of large towns, to attract birds and induce them to nest. In the first place, the nests and eggs of the English sparrow should be destroyed whenever found. Stray cats should be kept from harming birds. Pieces of meat, bones, and suet, when hung in the trees in winter time, and crumbs and grains scattered about, will serve to attract the winter visitants and, when thus attracted, these birds devour great numbers of the eggs and insects in the hibernating stages that during the following season would attack the fruit and shade trees. And finally, any ingenious boy can construct and put in the trees bird houses that in the springtime would become the

nesting places of bluebirds, wrens, tree swallows, and martins.1 (Fig. 77.)

1 For other methods of encouraging birds see Weed and Dearborn, "Birds in their Relations to Man," pp. 304-315. Trafton, "Methods of Attracting Birds," and leaflets of National Association of Audubon Societies, 1974 Broadway, N. Y., e.g. No. 16 (Winter Feeding of Wild Birds) and No. 18 (Putting up Bird Boxes), 1 cent each.

A. Regions and appendages. The frog's body consists of two principal parts, or regions; namely, the head and trunk. The line of union between the two regions is just in front of the anterior appendages (arms).

1. Locate the appendages (arms and legs) attached to the trunk.

2. Name and locate the organs that you find on the head, giving the number of each.

B. Breathing organs.

1. Describe the location of the nostrils on the head.
2. Examine a preserved specimen in which a stiff bristle
has been passed through one of the nostrils.

a. Tell what was done.

b. Into what cavity has the bristle emerged?

c. (Optional.) What is one difference, therefore, between the nostrils of a fish and of a frog? (See 102, 2 b.)

d. In what region (anterior or posterior) of the roof of the mouth cavity are the inner openings of the nostrils located?

3. (Demonstration.) Just back of the tongue there is a narrow opening that leads into the windpipe (trachea). This opening is called the glottis.

a. Locate the glottis.

b. Does the glottis extend lengthwise or crosswise of the mouth cavity?

c. Into what does the glottis open?

4. Examine a dissected frog prepared in such a way as

to show the lungs.

a. State the location of the lungs with reference to the head and the cavity of the trunk.

b. Describe the appearance of the lungs.

c. Insert the end of a glass tube, that has been drawn out to a small diameter, into the glottis

opening and blow air into the lungs. Describe what you have done and state the result.

5. Name in order the openings, the cavity, and the tube through which the air must pass in order to reach the lungs.

C. Breathing movements.

1. Place a frog in a glass jar with an inch or two of water and watch the action of the floor of the mouth.

This is one of the breathing movements. Describe this breathing movement of the frog. 2. There are two breathing movements of the sides of the trunk, one a very active inward and outward movement, and the other a very slight inward and outward movement. When you have seen these two kinds of movements of the sides, describe them and state which kind occurs the more frequently.

D. How the frog exhales.

1. What effect will the active inward movement of the sides have upon

a. The size of the body cavity?

b. The size of the lungs?

c. The pressure of the air in the lungs?

2. When the sides of the trunk move actively inward, will the air move into the lungs or out? Why? 3. Through what passages will the air go from the lungs to the outside of the frog?

E. How the frog inhales.

1. When the floor of the mouth moves downward

a. Will the size of the mouth cavity be made larger or smaller?

b. If the nostrils are now open will the air move into the mouth cavity or out? Why?

2. When the floor of the mouth is raised

a. Will the size of the mouth cavity be increased or decreased?

b. Will the pressure of the air in the mouth cavity be increased or decreased?

c. If both the nostrils and the glottis are now open, in what directions will air be forced?

d. What causes the slight outward movements of the sides of the trunk in the region of the lungs?

F. How the lungs are fitted for breathing organs. (Suggested as home work.)

When the lungs are inflated (see B, 4 above) they look like bags (Fig. 80). The lungs are hollow, and their walls are composed of thin material. In these membranous walls are thinwalled blood vessels known as capillaries. The heart forces blood that has come from the body into these capillaries of the lungs, and then back to the heart. Bearing in mind that respiration in animals is essentially the same as in plants (P. B., 82)

1. State what waste substance the blood brings to the
lungs to be given off from the capillaries.
2. What gas will the blood in the capillaries take up
from the air in the lungs?

3. How are the walls of the lungs and of the capillaries
of the lungs fitted by structure to make this
interchange of gases possible?

G. Food-getting.

To the Teacher. - Select a number of as large preserved or freshly killed frogs as you can get. Open the jaws as far as possible and keep them in this position by means of small pieces of wood.