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ADVENTURES WITH A MICROSCOPE
By Richard Headstrom
Dover Publications, Inc.Copyright © 1941 Richard Headstrom
All rights reserved.
We Examine Some Common Objects
For our first adventure we shall examine a few simple and common objects in order to get the "feel" of the microscope and the "hang" of its use. I know of no object more common or more easily obtainable than a hair from one's own head. So we will proceed to pull one out and place it on a slide in a drop of water. Then cover it with a cover glass, which we handle by means of a pair of fine-pointed curved forceps. Transferring the slide to the stage of the microscope, we examine it. We find it appears as shown in Figure 2.
Having satisfied ourselves as to what a hair looks like, we next proceed to examine an air bubble. To obtain such a bubble, we place on a clean slide a small fragment of blotting paper, torn from a larger piece so that it will have rough frayed edges. We wet it with water, using a glass rod for the purpose. Small air bubbles will be entangled in the fibers of the paper. Then cover the whole with a clean cover glass. On viewing the air bubbles we shall find that they appear as dark spots with shining centers. If we focus to different parts of a bubble, we will obtain different effects. Should we focus the objective to the middle of the bubble, the center of the image is seen to be very bright—indeed, brighter than the rest of the field (Figure 3A). We also find that it is surrounded by a grayish zone, and a somewhat broad black ring interrupted by one or more brighter circles, and that around the black ring are again one or more concentric circles brighter than the field.
If we focus to the bottom of the bubble we shall see that the central white circle diminishes and becomes brighter (Figure 3B), that its margin is sharper, and that it is surrounded by a very broad black ring which has on its periphery one or more diffraction circles.
And lastly, on focusing to the upper surface of the bubble, we shall note that the central circle increases in size, and is surrounded by a greater or lesser number of rings of various shades of gray, around which is a black ring but narrower than those that we found in the other two positions of the objective. (Figure 3C)
Fish scales are easily obtainable and also make beautiful objects for low powers. As they are often coated with a tenacious mucous material, this should first be removed by washing in a solution of caustic potash. The fish scales, like the piece of hair which we examined, should also be viewed in water. Figure 4 shows a scale from the herring.
Many of the smaller kinds of plant seeds are very curious-looking and some of them are extremely beautiful when viewed with a low power. The seed of the poppy, for instance, will appear as having a number of hexagonal pits on its surface (Figure 5). That of the snapdragon is strangely irregular in shape, while that of the carrot reminds one of a starfish. As you examine others that may be handy you will observe that they all have more or less individual characteristics.CHAPTER 2
We Become Crystal Gazers
Do not let the heading of this adventure mislead you. We are not going to peer into such crystals as fortune tellers use, in which they claim to be able to predict that some rich relative is going to leave you money, or some equally nonsensical bosh. Our crystals are to be the tiny geometrical bodies of which many substances are composed. Little do you realize, perhaps, that as you dissolve a spoonful of sugar in your coffee or sprinkle some salt on your food, you unwittingly are destroying thousands of beautiful tiny gems.
Perhaps you already know that both of these substances exist in crystalline form. On the other hand, you may be a doubting Thomas, or, like the man from Missouri, you want to be shown. In either case, let us examine a few particles of both substances, as I am quite sure you will want to view some of the most beautiful objects to be seen with the microscope.
Now, if we look at sugar or salt as it comes from the grocery store, I am afraid we wouldn't see much worth looking at, and so it becomes necessary for us to prepare our crystals, which is a very easy thing to do. To obtain such crystals, we simply dissolve some sugar or salt in a little hot water until we find that the water will not dissolve any more. We then transfer a drop or two of each solution to a clean slide and wait until the excess water has evaporated. When most of the water seems to have disappeared, we transfer the slide to the stage of the microscope. If we examine the slide containing the salt crystals first, we shall find that we have a number of little crystal cubes. Perhaps we shall also find some crystals which have departed somewhat from the cubic form, the departure in such instances being due to impurities in the water or salt. If we used iodized salt we should also find some colored crystals of iodine. But if the salt is chemically pure we should see nothing but perfect cubes.
We next examine the sugar, but in this case we shall be less able to see any definite arrangement of the crystals, as sugar does not crystallize at once from a saturated solution in water. If we set the slide aside for a day or so the crystals will, at the end of that time, have formed.
Now, sugar and salt are not the only crystals we can obtain and examine; there is a vast number of others such as alum, borax, washing soda, potassium permanganate, iron sulphate and copper sulphate, to name but a few. These are all common and easily obtained, and are all soluble in water.
We can watch the crystals in the process of formation if we want to. All that is necessary is to transfer the slide to the microscope when most of the water appears to have evaporated, for it is at this point that crystallization begins. I am sure that you will find it a most interesting sight to see the first crystal take shape, to be followed by others, until there appears a number of these tiny glistening gems. Extremely beautiful crystals may be obtained from certain substances, such as potassium bichromate, for instance. Copper sulphate, if dissolved in gelatine, will form lovely fern-like crystals that for beauty will rival the ice crystals that form on window panes in extremely cold weather and which are so familiar to us. To dissolve the copper sulphate in gelatine, gently warm the gelatine to which is added an equal volume of water. When the gelatine has all dissolved, add the copper sulphate until the point is reached when no more will dissolve. Then proceed as before.
As you watch the crystal formation of various substances you will observe that the crystals assume a definite form, the form varying according to the substance used. The salt crystals, as we have seen, form a perfect cube. Alum, on the other hand, assumes the form of the octahedron, while potassium permanganate the rhombic form, and rock candy, which is pure sugar, the mono-symmetric form (Figure 6), names which may sound familiar to you, particularly if you have studied geometry.CHAPTER 3
We Hunt a OneEyed Monster
Our third adventure takes us on the quest for a oneeyed monster. If you remember your Greek mythology, there existed at one time a race of one-eyed giants called Cyclops. Actually, of course, the Cyclops never existed and perhaps it was just as well, for if they had been anything like the one-eyed monsters to be found in the microscopic world, called Cyclops after their fabled prototypes, the world would indeed have been a terrifying place to live in. The Cyclops of which we speak are nothing but water fleas, and to us they do not look very big, but to the other animals that inhabit the microscopic world they appear no doubt as terrifying, ferocious ogres.
They live in ponds and spring pools and all we need in order to catch them is a wide-mouthed bottle. Armed with this, we make our way to the nearest pond or pool, and submerging the bottle in the water fill it almost to the top, being sure to gather up some of the mud and dead leaves, for it is among such things that the Cyclops hide. They are visible to the naked eye, and if we hold the bottle up to the light we should see them swimming about—little dots darting here and there, steadily and tirelessly.
But though we can see them with the naked eye, it is only under the microscope that we can see what they really look like. So we return home with our "catch" and set up our microscope. The next step is to transfer one of these one-eyed monsters from the bottle to a life slide which we place on the stage of the microscope. For this purpose all we need is a dipping tube. Placing the tip of the forefinger over the upper end, we dip the lower into the water and move it about until it is close to one of the Cyclops. Then we remove our finger, at which the water and Cyclops will rush up into the tube. Replacing the tip of the finger on the tube, we remove the tube. We find that the water and the imprisoned Cyclops will remain in the tube as long as we keep the finger on the upper opening. Placing the uncovered tip of the tube in the depression of the life slide, we remove the finger. Then the water will at once flow out, carrying Cyclops with it. By regulating the pressure through the movement of the finger, the water can be made to escape drop by drop, or in a sudden rush.
As Cyclops is a rather active little animal it may not remain quiet long enough for you to examine it properly. In that case you may quiet or anæsthetize it by placing in the depression of the life slide a solution of two parts of one per cent chloretone and five parts of water. You may also use this treatment for Daphnia which you will study in the next adventure.
We now have Cyclops where we want it, and so we adjust the microscope and examine it. As you will observe, it looks something like a miniature lobster (Figure 7). Indeed, it not only looks like a lobster but, as a matter of fact, it is related to the lobster and such other animals as the shrimps and crabs, all of which have a hard shelly coating and for that reason are grouped together under the name of Crustacea, which is from the Latin crusta, skin.
You can spend many pleasant moments studying Cyclops and watching it move about, which it does by means of specially designed swimming feet. But first of all can you find its solitary eye, which gives it its name? Look carefully at the head and you will see it as a dark spot. And do you, by any chance, find two pear-shaped masses attached to the body, one on each side of the tail-like appendage which extends out from the tip of the abdomen? If you do, then you have caught a female, for the masses are eggs. In time the eggs will hatch, and if you can manage to keep them alive you will soon have a whole family of these little oneeyed monsters.
But here I must add a note of warning lest you think, when you see the young swimming about, that you have come across some other species of animal, for when the young Cyclops (Figure 8) hatch they do not look anything like their mother. It is only after they have changed their skin several times that they begin to resemble their parent. So do not be fooled into thinking that the young Cyclops are entirely different animals, which is exactly what they were believed to be until they were seen leaving their eggs. Then their true character was discovered.CHAPTER 4
We Learn the Meaning of Privacy
Much as we may have enjoyed catching and watching Cyclops, there is another water flea which is perhaps more interesting to study, because we can see its inside, as well as outside, parts. Strangely enough, this water flea answers to the sissified name of Daphnia, but it is not a sissy at all, and I daresay that to the other inhabitants of the microscopic world it is a big bully, especially as it lives within a shell and goes about like a knight in armor.
Daphnia lives in the same sort of habitat as Cyclops, and can be caught in the same way. Like Cyclops, it is also visible to the naked eye and can easily be recognized from the illustration (Figure 9). It moves about quite rapidly, but you ought not to have much difficulty in capturing one with the dipping tube and transferring it to the life slide. To be able to observe it at length it is necessary, however, to restrict its activity, and to keep it within range of the microscope, so do not give it too much water in which to swim about.
This little animal is a veritable dynamo, for if you watch it closely you will see that every part of it, both inside and outside, appears to be moving. Do you notice its rapidly beating legs on the lower part of its body? But these are not legs at all, as we understand them. They are not used to walk or swim with, but to direct food into the animal's mouth as well as a stream of water which contains a certain amount of dissolved oxygen without which it could not live.
Perhaps you do not realize what a wonderful sight you are witnessing. But you will when I point out that here you have a complete view of a fairly complicated organic machine in operation. If you study Daphnia carefully you can see the passage of food through the alimentary tract, the blood flowing through the body, and even the contractions of the heart. And if you should happen to be looking at a female Daphnia, you will also see the eggs which she carries in her little pocket, and which will appear as little dark specks massed together.
Next time you hear people remark about the privacy of goldfish, tell them about Daphnia. Why, this poor little water flea's life is just one big open book, for we can even see what goes on inside of it. The goldfish, at least, have that much privacy.CHAPTER 5
We Follow in the Footsteps of Hercules
Hercules, as you may recall, was an ancient Greek hero who performed prodigious feats of valor. Especially noteworthy among his exploits was his slaying of the nine-headed monster Hydra which lived in the Lake of Lerna, where it was making itself unpleasantly active. Now we do not profess to be a hero like the mythological Hercules, but we shall try to follow in his footsteps and also hunt the Hydra, but with a different purpose.
Our Hydra, of course, is not a monster like the one that terrified the inhabitants of ancient Greece, but a little fresh-water animal which we will find attached to the stems and leaves of underwater plants.
Although it is only under the microscope that we can really watch its activities, it can readily be seen with the naked eye. It looks much like a short, thick thread unraveled at one end. It is abundant in ponds and streams, where it may be found attached by one end to aquatic vegetation, especially to the rootlets of the small floating plants known as Duckweed.
As you will find when you examine it under the microscope (Figure 10), Hydra is really a hollow tube, attached by a basal disc at one end and with a mouth opening at the other, around which are arranged six to ten smaller tubes called tentacles. The entire animal is elastic, and, anchored to some aquatic plant, or other submerged object, it contracts and expands its body at will, meanwhile weaving its tentacles about in search of food. And woe to any victim that comes within their reach, for the tentacles, like those of the jelly-fish, are provided with stinging cells which shoot poisonous barbs into the delicate flesh of the prey.
Excerpted from ADVENTURES WITH A MICROSCOPE by Richard Headstrom. Copyright © 1941 Richard Headstrom. Excerpted by permission of Dover Publications, Inc..
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