Laboratory manual for human physiology : experimental studies in hygiene, sanitation and physiology

Front matter

. HARTMAN.

WORLD BOOK COMPANY z* a en ae, = ae a a S| _ ee

NEW-WORLD SCIENCE SERIES

Section I. Organization Of Living Things

EXERCISE I. MATTER, INORGANIC AND ORGANIC. (CLASS WORK)

Material: A pebble; quartz or other crystals; pieces of iron, cotton, and wool; a living plant; a living animal, such as an insect.

Procedure: Discuss the properties of each object selected. After consulting a textbook of Physics, define matter and name some of the properties of matter.

Define living and non-living matter, naming appropriate examples. Name some of the properties of matter common to both living and non-living things. Name some of the more obvious properties possessed by living things.

Heat each non-living object mentioned above over a flame and note which FIG. 1. Alaboratoryblow- Objects char (become black). Charring torch or Bunsen burner. A indicates the presence of carbon, a conead ee ae stituent of organic matter. All organic lineis used as fuel. The Matter is derived from living things. burner can be set undera Define organic; inorganic. To what is Mey be laced. the color of black soil due? Show how

coal is organic in its nature. Which parts of your desk are organic? Which are inorganic? Mention three other organic and three other inorganic objects.

Votes: Answer the questions asked in this exercise. Give examples with each definition.

EXERCISE 2. THE CELL AS THE UNIT OF STRUCTURE OF LIVING THINGS. (DEMONSTRATION)

Experiment a. How to cut a section and mount it for microscopic study.

Apparatus and material: “ Microscope; slides and cover glasses; clear water and a pipette; sharp scalpel or section razor; elder pith, potato, or other object to be sectioned for study; a clean, soft rag such as a threadbare handkerchief ; dissecting needles ; a pair of forceps.

Procedure: Clean several slides and cover glasses. The cover glasses are easily cleaned if first dipped in alcohol.

Place a drop of water ona slide. All objects studied should be mounted in a liquid medium, usually a drop of water or a drop of staining solution. The liquid serves to hold the section in place and to make the object appear somewhat clearer to view.

To cut a section, hold a small block of potato or elder pith between the thumb and index finger of the left hand and cut the thinnest possible section with a sharp knife or a section razor held in the right hand. If the section razor is used, the blade may be made to slide over the tip of the middle finger of the left hand as the razor is pushed through the object in cutting the section. The section may be cut wedge-shaped ; that is, a little thicker at one end and as thin as possible at the other. The section would then taper to almost nothing at one edge. It is at this thinnest part that the best view of the cells can be had under the microscope.

Several sections may be cut in this way and placed in the drop of water on the slide. With dissecting needles the sections are spread out so that a clear view may be had of each piece. The cover glass is now dropped over the sections.

To avoid imprisoning air bubbles, hold the cover glass by one edge with a’pair,of forceps, apply it to the:drop of water, first at the opposite edge, and then allow it to fall upon the slide gradually. A little practice will enable one to do this skillfully. Should the drop of water prove too small to reach to the edges of the cover glass, it is not necessary to raise the cover glass in order to drive out the air. Apply a small drop of water to one edge of the cover glass. The water will enter by capillary attraction and the space under the glass will be filled. Merely applying the liquid to the edge will suffice. If too much water has been added, the surplus may be drained off by applying a small piece of absorbent paper to the edge.

The specimen is now ready for study. It is presumed that the teacher will manipulate the microscope and focus it upon the object for the pupil. The teacher should, however, show the pupil how the sections are prepared and mounted and how the microscope is manipulated. |

The teacher should teach the names of the important parts of the microscope to the pupils: base, pillar, mirror, drawtube, oculars or eyepieces, objectives, stage, diaphragm, coarse and fine adjustments. The pupil should understand how the light is reflected by the mirror and made to pass up through the drawtube and the lenses, and how it illuminates the object which is mounted on the slide and placed over the hole in the stage. The teacher should emphasize the fact that there are objectives of low and high powers. The lowpower objective is in focus when about one third of an inch above the cover glass of the preparation which is being studied, whereas the high-power objective, when in focus, is very near the object and hence is in greater danger of collision with the cover glass. The pupils should be allowed to see the same object through both low and high powers in order to form a general estimate of their relative magnifying power.

The following hints will prove helpful: (1) Do not use the high power when the low power will suffice. (2) If the high power is used, always focus with the low power first, thus finding the object and placing it in the center of the field. (3) Do not focus dow while looking through the instrument. (4) After turning on the high power turn it down so as almost to touch the cover glass. Determine this point by placing the eye ona level with the stage of the microscope. Then with the eye at the eyepiece, focus p until the ie ilo comes into focus.

The teacher should have at hand one or more copies of a pamphlet on ‘“ How to Use the Microscope,” published for free distribution by the company whose microscope he uses. A wall chart (also free) illustrating the instrument in section and in perspective should be owned by the school, as it will facilitate the study of the microscope.

Notes: Sketch the outline of a compound microscope and name the parts from the wall chart. Describe how a section is cut and mounted for study.

Experiment b. Pith cells of elder.

Apparatus and material: As in a, including pith of elder or corn.

Procedure: Make the thinnest possible free-hand section of elder or corn pith and mount it in a drop of water as described in a. Study with low and high powers. Note the glass-like cell walls. As these cells are dead, the protoplasmic contents are absent. Cork cells may be studied in the same way. A very thin section of potato may also be studied. Note here also the very thin glass-like cell walls and the elliptical or oval starch grains of various sizes within the cells. The starch grains are more easily seen than the cell walls. Each cell may contain from a few to several dozen starch grains (Ritchie, Fig. 61).

The cells of plants are large and have their thick, stiff walls composed of a substance called cellulose, while animal cells have thin, flexible walls composed of albumen or they have no walls at ali, as in the case of the white blood corpuscles and nerve cells. That all living things are composed of cells is known as the “cell theory.” It was first announced in 1838. On account of the large size and stiff walls of plant cells, especially wood cells, the cellular structure of plants was first discovered. Soon after this discovery it was found that the bodies of animals are also composed of cells.

Notes: Sketch the cell walls of elder pith, potato, or cork.

Experiment c. An animal cell.

Apparatus and material: Microscope and prepared slide of ovary of cat or rat; egg of sea urchin or starfish or section of liver.

Procedure; Place a slide under the microscope and select one or more typical cells from the specimen. It would be well, if more than one microscope is available, to mount several typical cells. An egg cell from the ovary of a cat or rat or the egg of a starfish is an excellent example. Note the nucleus and other parts of the cell. Compare Ritchie, Fig. 1, A and BS.

Note: Sketch one or more typical cells and name the parts.

Experiment d. Cells from the mouth.

Apparatus and material: Microscope; slide and cover glass ; scalpel or other knife; methyl-green solution.

ORGANIZATION OF LIVING THINGS II

Procedure: Clean a scalpel and sterilize it by holding it in a flame fora moment. Scrape some cells from the inside of your own cheek. Smear the scraping ona slide and cover with acover glass. Find large, flat cells, hardly visible at first on account of their great thinness and transparency. Note nuclei. (See Fig. 75, The Human Body and Its Eenmies, page 121.) Add a drop of methyl-green solution, which stains the nuclei and makes them appear more distinct. (The solution will run under the cover glass as soon as the drop touches the edge of the glass; the glass need not, therefore, be raised to add the solution. )

Votes: Sketch several flat cells from the mouth as they appear under the microscope.

Experiment e. Paramecium, a one-celled animal.

Apparatus and material: Microscope; slide and cover glass; 2 % acetic acid solution ; 8 % gelatin solution (not absolutely necessary); culture of Paramecium.

Procedure: Make a hay infusion or hay “tea” by steeping a handful of chopped hay in a pan of warm water. Set it aside in a warm place, partly covered with a glass plate to prevent too rapid evaporation. Ina few days decay will set in, due to the action of the rapidly multiplying bacteria. Later, Paramecia will abound in countless numbers, feeding upon the bacteria. The white scum on the surface of the culture will be especially rich in the animalcules. |

Mount a drop of the infusion on a slide and note the Protozoa (see Ritchie, pages 5 and 285) as well as the bacteria. The former will be seen as comparatively large, one-celled animals swimming actively about in the liquid. The bacteria are very tiny rod-shaped objects swimming about with a zigzag or vibrating movement.

I2 LABORATORY MANUAL

If mounted in a drop of gelatine solution (about 8 %) which is just liquid at room temperature, the swimming of the Paramecia will be retarded and their study greatly facilitated. Note the action of the cilia (Ritchie, Fig. 3). After the living animals have been studied, kill them by adding to the slide a drop of 2 % acetic acid. Note that the cilia are thrown out as the Paramecia die from the effects of the acid.

Notes : Sketch several Paramecia with their cilia.

EXERCISE 3. REPRODUCTION OF CELLS. (DEMONSTRATION)

Experiment a. Paramecium.

Apparatus and material: Same as Exercise 2, e.

Procedure: In the Paramecium culture described in the preceding exercise (2, e) note dividing individuals as shown in Ritchie, Fig. 3; with a little perseverance a number of these will be found. When found, kill with 2 % acetic acid, otherwise the individual animalcule to be shown will swim out of the field of vision.

Notes: Sketch a dividing Paramecium.

Experiment b. Yeast.

Apparatus and material: Microscope; slides and cover glasses; yeast cake; 10% molasses solution; the apparatus shown in Fig. 2.

Procedure: Make a yeast culture as follows: Fill a wide-mouthed bottle with 10% molasses solution (10 parts of molasses in 90 parts of water) and add to this one fourth of a yeast cake. Place a little molasses solution in a dish and invert the bottle in the dish (Fig. 2), taking care that the bottle remains full. To accomplish this, cover the mouth of the bottle with cardboard, hold the cardboard in place while inverting the bottle, and remove the cardboard after the inversion has been accomplished. The mouth of the bottle should be raised a little above the bottom of the dish by a couple of nails or matches. Set the culture aside in a warm place.

At the end of 24 hours study the yeast cells in a drop of liquid taken from the surface or from the bottom of the liquid in the dish. Note budding yeast cells as shown in Ritchie, Fig. 112. The yeastjj’cells multiply by growing “ buds,” each of which becomes a new yeast plant.

FIG. 2, The fermentation of molasses by yeast plants. See Exercise 3, b.

Notes : Sketch several “ budding” yeast plants.

Experiment c. Cartilage cells.

Apparatus and material ; Microscope and prepared section of cartilage tissue.

Procedure: Study prepared slide of cartilage tissue. Note the cells within pockets or lacunz of the tissue. Note that some lacunze contain more than one cell; these cells are dividing or multiplying. (See Ritchie, Fig. 26.)

Notes : Sketch several dividing cartilage cells.

Experiment d. Sea-urchin eggs.

Apparatus and material: Microscope and prepared slide of dividing sea-urchin or starfish eggs.

Procedure: Study prepared slide of dividing sea-urchin eggs, showing 2-, 4- 8-, 16-, 32- and more cell stages. Every animal or plant begins as a one-celled form; namely, from an egg produced by the mother plant or animal. This cell multiplies, in higher forms, until the complex body of the plant or animal results. (See Ritchie, page 6.)

Votes : Sketch eggs in different stages of division.

EXERCISE 4. ARRANGEMENT OF CELLS INTO TISSUES. (DEMONSTRATION)

Experiment a. Cartilage tissue.

Apparatus and material: Microscope; prepared slide of cartilage tissue (as in Exercise 3, c); also, if desired, fresh cartilage from the end of a bone; sectioning knife or razor; slides and cover glasses.

Procedure: Study the preparation of cartilage tissue. Note that the tissue consists of cells and the ground substance between the cells. (See Ritchie, Fig. 26, a and 0.)

It is instructive also to study a fresh specimen of cartilage tissue. Cut a free-hand section of cartilage from the end of a long bone, e.g. of a “drumstick.” The femur of a frog soaked in alcohol or formaldehyde will do very well. Study the section mounted in a drop of water or dilute alcohol; compare with the stained preparation. (Study Ritchie, page 59, footnote.)

Votes : Make a drawing of cartilage tissue.

Experiment b. Connective tissue.

Apparatus and material: Microscope; slides and cover glasses; dissecting instruments; Ringer’s solution; methyl-green solution; dead mouse; piece of: ligament from back of neck of ox.

Procedure : How to kill an animal: Under no circumstances should an animal be experimented upon alive or tortured in any way. When the experimenter is ready, the animal

ORGANIZATION OF LIVING THINGS I5 should be killed by chloroforming it. Select an air-tight box or a glass or earthenware jar suitable to the size of the animal. A five-gallon jar is a good size for a chloroforming jar. Drop a rag or tuft of cotton saturated with chloroform into the bottom of the jar. Then place the animal in the jar and cover it. The animal will soon be dead.

Cut off and skin the tail of the mouse. Long white tendons are now visible running along the tail. Pull off a tendon with a pair of forceps and place it in a drop of water on a slide. With dissecting needles tease out the tendon, z.e. tear it apart into fine shreds. Cover the preparation with a cover glass and study the tissue under the microscope. Note the fibers. Tease out another bit of tendon in methyl-green. Are cells now visible in such a stained preparation? (See Ritchie, page 8.) The tendon just studied is white connective tissue and is inelastic, z.e. it will not stretch, as may be demonstrated with a piece of the loose tendons from the leg of an ox ora pig. Elastic (yellow) connective tissue may be taken from the large ligament found in the neck of cattle. This ligament is called the Agamentum nuche. It serves to hold up the head. Being elastic, it stretches when the animal wishes to lower the head, as when grazing. Obtain a piece of this ligament from a butcher. Demonstrate its elastic qualities. If desired, a bit of this tissue may be treated and studied as described above for the preparation of a tendon from the tail of a mouse. The connective tissue layer under the skin and the connective tissue framework of most of the tissues and organs contains an admixture of yellow elastic fibers.

NVotes: Sketch connective tissue and show how the footnote, Ritchie, page 59, applies to this tissue.

Experiment c. Epithelial tissue.

Apparatus and material: Microscope; prepared slides of skin, of trachea or esophagus and of stomach or intestine.

Procedure: In epithelial tissue the cells are arranged like the bricks of apavement. In some organs the epithelial tissue serves to cover surfaces; as, e.g. in the outer skin (Ritchie, Figs. 5, 93, 94, 96, 113, 116). In other organs the tissue lines cavities (Figs. 6, 47, 49, 51, 55, 76). These figures should be studied by the class before the slides are studied. The teacher will then focus the microscope on the epidermis of the skin, on the lining of the trachea (or the esophagus), and on the lining of the stomach (or the intestine). Note that epithelial tissue of the skin is many cells thick and that of the stomach and intestine only one cell thick.

Notes: Sketch a portion of each organ studied, showing the epithelial tissue.

Experiment d. Muscle tissue.

Apparatus and material: Microscope; slides and cover glasses; dissecting needles; Ringer’s solution ; small piece of muscle from breast of cooked {chicken; also portion of muscular wall of chicken’s gizzard.

Procedure: Pull out a very small bundle of muscle from the breast of the chicken and tease out the specimen into the finest possible shreds. Study it under the high power of the microscope. Can you see the muscle fiber with its cross stripes as represented in Ritchie, Fig. 35, B ?

Treat the muscle from the gizzard in the same manner. The muscle fibers here do not exhibit cross stripes; they are smooth (unstriped) or involuntary muscle fibers. Can you find muscle cells as shown at the top of Ritchie, Fig. 5? Explain how the cells fit together to make a tissue.

Notes: Sketch several muscle fibers of each kind, as seen. Tell where each kind of fiber is taken from and describe how it was prepared for study.

Experiment e. Nerve tissue.

Apparatus and material: Same as in preceding experiment, substituting a nerve of some animal for a muscle.

Procedure: A nerve may be found as a shining white cord, not so glistening or so tough as a tendon, in the flesh of any animal. Tease out a portion of a nerve on a slide and study it. Note the nerve fibers. No cells will be seen, for a nerve consists of fibers only, the cells being situated in central stations called ganglia or in the brain or spinal chord. (See Ritchie, Fig. 15.) The nerve cell could be studied in a prepared section of one of these organs.

Notes: Sketch a nerve which has been torn apart to show the fibers.

EXERCISE 5. ARRANGEMENT OF TISSUES INTO ORGANS. (CLASS WORK)

Experiment a. A muscle.

Material: A small muscle, such as a muscle of a toad ora frog ; dissecting needles.

Procedure ; Dissect a muscle and note as many kinds of tissue as you can. (Cf. Ritchie, Figs. 35 and 36.)

Notes: Describe this experiment and make a list of the tissues found.

Experiment b. Other organs. (Home work.)

Material: Ritchie, Figures 49, 91, and 93-96.

Notes: From a study of the appropriate figures in Ritchie make a ist of tissues that enter into the formation of the stomach, the kidney, and the skin.

EXERCISE 6. PLAN OF THE BODY. ARRANGEMENT OF ORGANS. (CLASS WORK)

Experiment a. A simple plan: Hydra.

Apparatus and material: Microscope, and prepared cross section of hydra.

Procedure: Study a cross section of a hydra under the low power of the microscope. Note the ring of cells. This is the wall of the animal, which consists merely of a hollow sack, attached at one end and open at the other.

For further studies of the Hydra consult a textbook of Zoology.

Notes : Sketch a cross section of the Hydra.

Experiment b. The double-tube plan: the earthworm.

Apparatus and material: Microscope; hand lens; and prepared cross section of an earthworm.

Procedure: Study the cross section of an earthworm under a hand lens and under the microscope. Note the body wall (largely muscular) on the outside and the intestine on the inside. The latter is suspended from the wall above by a mesentery. The space between the body wall and the intestine is the body cavity. The plan of structure of the earthworm is thus that of a tube within a tube.

Study Ritchie, Fig. 9, and note how the human body conforms to the general ‘‘double-tube”’ plan of structure.

Experiment c. Exo-skeleton and endo-skeleton.

Apparatus and material: Insects, such as grasshoppers, crickets, or cockroaches; a frog or toad; dissecting instruments; dissecting boards or pans; killing jar or box; chloroform. What insect is used depends upon the season of the year. In spring and fall grasshoppers are available; in winter cockroaches may be caught in grocery stores, bakery shops, and other places, especially at night. Toads may be found at night in gardens or on lawns, and frogs may be captured about springs or ponds at certain seasons.

Procedure: The toad or the frog may be skinned thus: slit the skin lengthwise from the jaw back. Then slit it across the middle of the body. The skin may now be pulled off like a glove. Cut off a leg of an insect and a leg of a frog. Study the cut ends. Note that the insect has the skeleton on the outside and the muscles on the inside. Compare the condition in the frog with that in the insect. Feel your own arm and note the relation of bone to muscle. (See Ritchie, Fig. 39.)

Study Ritchie, Fig. 9. Note that the intestines are in the ventral cavity, and that the spinal cord and brain (central nervous system) are on the dorsal side. (See Ritchie, page 16, footnote.)

Lay the frog on its back and open the body cavity by slitting open the ventral wall of the abdomen. Note the intestine. Find the backbone. Turn the frog over and cut open the backbone, exposing the spinal cord. (Do not injure the spinal cord, for the same specimen should be used again.) It is thus seen that the frog, as well as the human being, has the central nervous system dorsal to the intestine.

Lay the cockroach or grasshopper on its ventral surface in a dissecting tray. This is sometimes best done with enough water in the tray to cover the insect, worm, etc. The insect may be fastened to the beeswax by pins. With a pair of scissors cut off the dorsal wall, thus exposing the intestine and other organs in the body cavity. Push them aside and note the “nerve chain” on the ventral surface. The nerve chain is seen to consist of nerve fibers and a series of ganglia, or knots of nerve tissue. It is thus found that the insect has the nervous system ventral to the intestine.

Notes : Sketch a longitudinal section of a frog after the plan of Ritchie, Fig. 9, and beside it place a sketch of a similar section of the insect. Let each drawing show body wall, skeleton, nerve chain, and intestine.

EXERCISE 7. THE CLASSIFICATION OF VERTEBRATES. (HOME WORK)

Experiment a. The classes of vertebrates.

Reduce the diagram, Ritchie, Fig. 11, to outline form, adding to the outline the characteristics of the five great classes of vertebrates according to footnote, page 18. To what class oes man belong? Why?

Experiment b. Comparison of man with other mammals.

Material: Illustrations in Ritchie; a textbook in Zodlogy ; skeletons or parts of skeletons of various animals brought into the laboratory by the pupils.

Notes: Write out a comparison of man and other mammals as to: (1) The position of the axis of the body. (2) The various means of locomotion among mammals and the resulting differences in fore and hind limbs. (See Ritchie, Fig. 33.) Why are the fore and hind limbs much alike in the horse but different in man, the bat, the whale, and the kangaroo. (3) The elimination of the tail as a functional organ. (4) The increase of the hemispheres of the brain. (5) The change of facial angle. (Cf. Ritchie, Figs. 17 and 32.) The study of the classification of mammals may be pursued further by reference to textbooks on Zoology.

EXERCISE 8, GENERAL VIEW OF THE NERVOUS SYSTEM. (DEMONSTRATION)

(To tllustrate Ritchie, Chapter lll )

Experiment a. The central nervous system.

Apparatus and material: The toad used in Exercise 6, ¢, above; dissecting instruments.

Procedure: Continue the dissection of the nervous system as begun in Exercise 6, c, by cutting away enough of the vertebrze on the dorsal side of the animal to show the entire spinal cord. Remove also the roof of the skull, exposing the brain. A strong pair of fine-pointed scissors will be found useful for removing the bone, piece by piece. The dissection, if well done, should be preserved in 5% formaldehyde and kept from year to year. The covering of the vessel may be sealed with paraffin to prevent evaporation of the formalin.

Notes : Sketch the central nervous system (brain and spinal cord) of the frog.

Experiment b. The sympathetic nervous system.

Apparatus and material: The toad used in the preceding experiment; dissecting instruments.

Procedure: Remove all the viscera of the animal. Lay it on its back. The dorsal wall of the ventral cavity is now in view. A careful search will disclose a chain of ganglia connected by nerves lying close against the dorsal wall of each side of the ridge which marks the spinal column. These two nerve chains with their fibers belong to the sympathetic nervous system (Ritchie, Fig. 105).

Votes : Sketch the sympathetic nerve chains of the frog.

Experiment c. Reflex action.

Apparatus and material; Frog or toad, recently killed ; 10% acetic acid.

Procedure: Stretch the hind leg of the frog and let go; the leg is drawn up. Touch the hind foot with a drop of 10% acetic acid; the foot is withdrawn. Touch the chest with a drop of acid. What is the result?

LVotes : Describe several experiments illustrating reflex action.

Experiment d. Function of a nerve.

Apparatus and material: The frog or toad used in the preceding experiment; a glass rod; the apparatus shown in Fig. 6.

Procedure: Lay bare the sciatic nerve as described in Exercise 22, a. Stimulate the nerve (1) by pinching it at a point as far from the foot as possible. What is the result ? Stimulate the nerve (2) by touching it with a hot iron. Stimulate the nerve (3) by applying an electric current from a dry cell. Do you observe any change in the nerve on stimulation? What is the function of anerve? Of what is a nerve composed? (Review Exercise 4, e, and see Ritchie, Fig. 15.) Name the three kinds of stimulation employed in this experiment to stimulate the nerve.

Votes: Answer the questions asked in this exercise. Describe how the experiments were performed, drawing figures where necessary.

Section II. The Organs Of Locomotion

EXERCISE 9. THE SKELETON. (CLASS WORK) ~

Experiment a. The human skeleton.

A human skeleton should be studied in connection with Ritchie, Chapter IV. If the school does not possess a specimen, it may be possible to borrow one from a physician of the community. Study advanced textbooks for suggestions. It will be well for the teacher to lecture to the class on the parts of the skeleton and their uses and peculiarities, illustrating each point by reference to the skeleton. A definite knowledge of the most important things to be noted in the skeleton may thus be acquired in a few periods.

Experiment b. Skeleton of a cat.

It is possible to illustrate many important features by using the skeleton of a mammal, such as the cat. To prepare a skeleton: Kill the cat by chloroforming it, skin it, remove the viscera without injuring the chest bones, and cut off all the flesh possible with a scalpel and scissors. Then boil the animal for a short while in the following “liquid soap”’ mixture: water 2000 c.c.; ammonia, 150 c.c.; saltpeter, 12 g.; laundry soap, 75 g. Boil the skeleton until the muscles have softened but the ligaments still hold together. If it is desired to disarticulate the skeleton, the bones must be boiled longer. It may be well to disarticulate the head and limbs before boiling. To prevent the vertebral column from coming to pieces, the vertebree may be “strung” on a strong piece of twine or on a wire which is run through the neural canal. With patience any pupil may make an excellent preparation of a skeleton. The pupils should be encouraged to bring the skeletons of various small animals. The school may thus easily acquire specimens of all the vertebrate limbs shown in Ritchie, Fig. 33.

EXERCISE I0. OBSERVATIONS ON THE SKELETON. (CLASS ; WORK )

Experiment a. Classification of the bones.

Material: A skeleton.

Procedure; On the human skeleton study the bones named in Ritchie, Chapter IV, and especially in Fig. 16. If only the skeleton of the cat is available, make out all the corresponding bones of the cat. Classify every bone (1) according to shape. and (2) according to use.