The clinical pathology of the blood of domesticated animals

Front matter

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Preface To The Second Edition

The purpose of this book is to furnish a text-book of hematology for the use of students and practitioners of veterinary medicine. It is also intended to render easily accessible for investigators data concerning the blood of the kinds of experimental animals commonly used.

Compared with the investigations made on the blood of man, but little has been done on the blood of domesticated animals. Some work, however, has been done. The results obtained are of more value than their mere amount would indicate because we have learned from the studies made that similar pathological processes produce changes in the blood similar to those produced by such processes in man. So the rich results obtained from man are made available to the veterinary practitioner.

Free use has been made in preparing this book of the standard works on the blood of man. Those of Ewing, Cabot, Da Costa, V. Limbeck, Naegeli and Grawitz were used most freely. References will be found in the text to the source from which material has been taken. A list of references is given at the end of each chapter for the use of advanced students.

In the first edition what was reported by different investigators as normal was given without indicating which of these the author considered more reliable. Undergraduate students and most practitioners can hardly be expected to know what to consider as normal when they find considerable variation. In this edition what is considered to be the normal for each species is stated. Tables summarizing the results obtained by the different investigations are also given.

Ithaca, N. Y.

Feb., 1917.

S. H. BURNETT.

vu

Table Of Contents

PAGE

List of Illustrations xiii

Introduction xv

CHAPTER I Procuring blood 1

Counting the leucocytes 8

Counting the blood plates 9

Estimation of the amount of hemoglobin 11

Tallqvist's hemoglobin scale 11

Gower's hemoglobinometer 12

Dare's hemoglobinometer 13

Fleischl-Miescher hemometer 15

Histological examination 16

In the fresh condition 16

In fixed and stained preparations 17

Differential counting of leucocytes 21

Test for glycogen 22

Test for fat 23

The total volume of blood and its oxygen capacity 23

The relative volume of corpuscles and of plasma 24

The specific gravity 25

The time of coagulation 25

Test for specific agglutinins or precipitins 26

Bacteriological examination of blood 26

Partial Ust of text-books on hematology 27

VARIATIONS IN RED CORPUSCLES AND HEMOGLOBIN

Blood from different portions of the vascular system 60

Polycythemia 61

Age 62

Sex 62

Pregnancy and parturition 63

High altitudes 64

CHAPTER V Leucocytosis 70

Digestion 70

Pregnancy and parturition 71

In the new born 72

Violent exercise, cold baths and massage 73

Inflammatory leucocytosis 73

Experimental leucocytosis 75

Post hemorrhagic leucocytosis 78

Ante mortem leucocytosis 79

Lymphocytosis 80

Eosinophilia 80

Basophilia. 82

Occurrence of myelocytes 82

Leucopenia 82

TABLE OF CONTENTS xi

SPECIFIC INFECTIOUS DISEASES DUE TO BACTERIA AND FUNGI

Strangles 100

Croupous pneumonia in horses 101

Takosis 102

Fowl cholera 103

Fowl typhoid 104

Anthrax 105

Glanders 108

Tuberculosis Ill

Tetanus 112

Actinomycosis 113

Botryomycosis 114

Herpes tonsurans 114

CHAPTER IX Spirochetosis 116

Rabies 117

Canine piroplasmosis , 123

Equine piroplasmosis 129

Ovine piroplasmosis 131

Babesia mutans 131 xii TABLE OF CONTENTS

PAGE

East coast fever 132

Piroplasmosis in cattle in Transcaucasia 133

Trypanosomatosis 133

Surra 135

Nagana 137

Dourine 138

Mai de caderas 139

Gambian horse sickness 142

Trypanosoma theileri 143

Chapter X Diseases Whose Cause Has Not Been Definitely Determined

Dog distemper 148

Rinderpest 148

Hog cholera 150

Equine infectious anemia 150

Rheumatism 152

CHAPTER XI Acariasis 155

Helminthiasis 153

Sclerostomatosis in horses 157

Trichinosis ; . 157

Filariasis in dogs 158

Teniasis 159

Uncinariasis 159

Oxyuris, Strongylus and Ascaris 159

Index 161

LIST OF ILLUSTRATIONS

PAGE

Plate I. Normal blood of animals 29

Plate II. Red corpuscles 30

Plate III. Blood of the domestic fowl 32

Plate IV. Lymphatic and mixed celled leukemia 88

FIGURES IN THE TEXT

Fig. 1. The Thoma hematocytometer 4

Fig. 6. Tallqvist's hemoglobin scale 11

Fig. 7. Gower's hemoglobinometer 12

Fig. 8. Dare's hemoglobinometer 14

Fig. 9. Fleischl-Miescher hemometer 15

Fig. 10. Spreading film on glass slide 17

Fig. 11. Blood of case of anthrax, cow 106

Fig. 12. Babesia bigemina 119

Fig. 13, Babesia canis 124

Fig. 14. Babesia mutans 132

Fig. 15. Theileria parva 133

Fig. 16. Trypasosoma evansi 136

Fig. 17. Trypanosoma brucei 137

Fig. 18. Trypanosoma equiperdum 139

Fig. 19. Trypanosoma equiperdum, mice 140

Fig. 20. Trypanosoma equinum 141

Fig. 21. Trypanosoma dimorphon 143

Fig. 22. Trypanosoma theileri 143

Fig. 23. Filaria immitis in blood, dog 158 xiu

Introduction

The blood may be considered as a tissue composed of a cellular part and an intercellular substance. The cellular part comprises the colored and white corpuscles and the plates while the intercellular substance consists of the fluid portion. The blood is a peculiar tissue in that it is in intimate relation with practically all the other tissues of the body, bringing substances to them and carrying away other substances. Thus the blood is affected by all the tissues. One might expect that the blood would give a good deal of information as to the state of the activities of the tissues; but at the present time comparatively little use is made of the chemical substances contained in the plasma. In the first place they are present in very small quantities, as an excess is prevented by prompt elimination; and in the second place many of these substances have very complicated structures. In fact the chemical make-up of the blood is but little known. In a clinical examination main reliance is placed on physical and histological rather than chemical methods.

The value of an examination of the blood varies in different conditions. In general it may afford sufficient information to make a diagnosis in a few diseases, such as leukemia, Texas fever, surra, anthrax and filariasis. It gives more or less valuable assistance in a very large number of conditions, as secondary anemia, sepsis, suppurative processes, intestinal helminthiasis and hemorrhagic diseases. Finding that the blood is normal is often a great help, as it enables one to differentiate from the diseases in which the blood is not normal. Hodgkin's disease is diagnosed by a blood examination, yet the blood is normal in the early stages, this serving to distingiush it from leukemia, which produces marked changes in the blood but has otherwise similar symptoms. Besides its value in diagnosis, the blood frequently gives most important indications as to prognosis and treatment and is of value in examinations for soundness. For example, in pneumonia there is ordinarily an increase in the number of leucocytes. If instead

XV xvi INTRODUCTION

of there being an increase the number is below the normal it is a bad sign. During the course of this disease the reappearance of the eosinophiles is a favorable sign, indicating that the crisis is passed. In an anemia in which the hemoglobin is much lessened while the number of red corpuscles remains nearly normal, the indications for a prompt improvement under the administration of iron are good; while but little improvement is to be expected when the amount of hemoglobin in each corpuscle is normal and practically no improvement when the hemoglobin index is above normal, iron being practically contraindicated in the more severe cases when the blood shows very large red corpuscles each having an increased amount of hemoglobin. In examinations for soundness the blood offers valuable aid, as has been pointed out by Moore. When an examination reveals that the blood is not normal a close search for the cause is indicated. The presence of disease, unsuspected it may be by the ordinary means of examination, may be shown by the blood. Though the fact that an animal's blood is normal is not indicative that the animal is sound, it is an added safeguard, and on the other hand an animal having an abnormal condition of the blood cannot be certified as being sound.

In interpreting the results of an examination of the blood it must be kept in mind that this is but one symptom. A diagnosis should be made after duly considering all of the symptoms available. The blood is not supposed to supplant other means of examination, but is to be used with them. In fact it will have a strong tendency to sharpen one's powers of observation for other symptoms.

THE CLINICAL PATHOLOGY OF THE BLOOD OF DOMESTICATED ANIMALS

THE CLINICAL PATHOLOGY OF THE BLOOD OP DOMESTICATED ANIMALS

•• CHAPTER I

Ordinarily a clinical examination of the blood consists of counting the red and white corpuscles, obtaining the amount of hemoglobin, and making a histological examination of stained specimens. Occasionally other information is desired, as the total volume of blood and its oxygen capacity, the relative volume of corpuscles and of plasma, the number of blood plates, the specific gravity, the time of coagulation, the presence of specific agglutinating or precipitating substances, and the presence of parasites.

Procuring the blood. Blood may be procured from any part of the body where the circulation is normal. Inflamed or edematous areas are especially to be avoided. A cold or bloodless part is unsuitable. If a cold part is warmed, sufficient time should be given to allow the circulation to become normal before procuring blood for examination. In the horse and cow the under side of the tail where free from hair, slightly to one side of the median line to avoid the middle coccygeal artery, is a convenient site, or if preferred, the rump or the side of the neck may be chosen; in smaller animals the lobe of the ear will be found suitable; in the domestic fowl the comb and in the pigeon the under surface of the wing are easily accessible and convenient.

Preparation of the site. The part from which blood is to be obtained should be washed with water, in the larger animals where the incision is to be made with a fleam, disinfected, and then dried with alcohol. Vigorous rubbing of the part should be avoided as it produces a transient local change in the blood. In case the neck, or other part in the horse or cow having long hair, is selected the hair may be parted and the skin, exposed in the parting, washed as indicated. It is not ordinarily necessary to shave the site.

Puncture. In the larger animals it is advisable to use a fleam or a scalpel for making the puncture as a blood lancet does not yield sufficient blood. In the smaller animals a blood lancet or straight surgeon's needle is preferable. Whatever instrument is used should be sharp. A dull needle or fleam causes more pain and affords less blood than one that is sharp. In the domestic fowl blood may be readily and easily secured by snipping off the tip of one of the points of the comb.

Securing the blood. Before making the puncture whatever apparatus or material is to be used should be ready and within reach so that there may be no unnecessary delay in securing the blood for examination. Slides for making smear preparations, the hemoglobinometer and the pipette for making the dilution should be clean and within reach. The bottle of diluting fluid should be unstoppered. A towel or clean cloth should be at hand. After the puncture is made the first three or four drops of blood should be wiped off. Then freshly exuded blood should be secured for examination, for counting the red corpuscles and leucocytes, for obtaining the hemoglobin value, for making smears for histological examination or for other kinds of examination. The more rapidly blood is secured for these several processes the better. Blood quickly changes when exposed to the air. Clotted blood is wholly unsuitable and even before it clots blood undergoes certain changes, some of which simulate changes found in pathological conditions. Blood should be obtained as nearly as possible in the condition in which it is in the blood vessels. After sufficient blood has been secured the edges of the wound in the larger animals should be held together for a few seconds until they adhere. On the following day it will require careful search to find the wound.

The red corpuscles are so numerous in the blood that it is necessary to dilute it considerably to be able to count them. The diluting fluid must be of such a nature that it will prevent coagulation, will not change the corpuscles and should be of such a specific gravity that the corpuscles will settle, not too rapidly or it will be difficult to get an even distribution of them in the counting chamber, nor too slowly or one will have to wait too long for them to settle. Toisson's fluid combines these qualities perhaps the best of the diluting fluids in use. It has an added advantage in that it stains the leucocj^tes, rendering it possible to count them in the same preparation with the red corpuscles. Toisson's fluid should be filtered before using as fungus will grow in it producing spores which may be confusing in making a leucocyte count. Hayem's fluid is also a suitable diluting fluid.

Under some conditions Toisson's fluid is not the best that may be used. Jones has called attention to the counts being lower with Toisson's fluid than with Hayem's in certain cases of severe anemia. He found that Toisson's fluid gave lower counts in cases of pernicious anemia in man and in experimental cases of anemia in rabbits produced by bleeding or by phenylhydrazin. It would be better to use Hayem's fluid in cases of severe anemia. It is not certain that the formula for Toisson's fluid is the best for the several species of animals.

Formulae:

Toisson's Fluid

Sodium sulphate 8 grams.

Sodium chloride 1 gm.

Glycerin, neutral 30 cc.

Distilled water 160 cc.

Methyl violet, 5B 025 gm.

Hayem's Fluid

Mercuric chloride 0.5 gm.

Sodium sulphate 5 gm.

Sodium chloride 1 gm.

Distilled water 200 cc.

While several methods of counting the corpuscles have been used, Thoma's hematocytometer, which is a combination of the older instruments of Malassez, Hayem and Gower, has come to be used as the most reliable.

The instrument consists of a counting chamber with an accurately polished piano-parallel cover glass and a diluting and mixing pipette. The counting chamber is a thick glass slide on which is cemented a square plate having a circular piece cut out of the center. In this circular space is fastened a small circular

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Fig. 1. The Thoma hematocytometer.

disc which is thinner than the surrounding plate. The distance from the top of the disc to the under surface of a cover glass placed on the plate is exactly 0.1 millimeter. The upper surface of the disc is ruled as shown in Fig. 2. The central square is ruled with lines aV nim. apart giving 400 squares each containing -^^^ sq. mm.

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Fig. 2. Thoma.

Fig. 3, Thoma, central ruling.

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Fig. 4. Zappert-Ewing. Fig. 5. Turck.

Rulings of Counting Chambers.

The Zappert-Ewing ruling, the one to use preferably, has besides this central 400 squares additional lines as shown in Fig. 4 giving a ruled space of nine sq. mm. With each instrument are thick and thin cover glasses with plane ground surfaces. The thick covers give more accurate results. The mixing pipette is a capillary tube divided into ten equal divisions and terminated by a bulb of 100 times the capacity of the tube. Thus when blood is drawn to the mark 1 on the tube and diluting fluid is drawn to the mark 101 a dilution of 1:100 is obtained. The bulb contains a glass bead to facilitate mixing the blood and diluting fluid. Attached to the pipette is a flexible rubber tube having a mouthpiece. The pipettes are made in a long and a short form. The longer form is preferable as the shorter form is constricted at the point rendering it liable to become clogged and making it very difficult to clean should it become clogged.

Method of using. The bottle of diluting fluid should be within reach and should be unstoppered. In using, the point of the pipette is immersed into a freshly exuded drop of blood. With gentle suction blood is drawn up to one of the divisions on the tube, the pipette is withdrawn and the blood on the outside of the tube quickly wiped off. As quickly as possible it is placed in the diluting fluid with the point well below the surface and the diluting fluid drawn in filling the pipette exactly to the mark 101. The blood and diluting fluid are then thoroughly mixed by shaking and rotating the pipette. Care must be taken to draw in fresh blood, the slightest clotting will necessitate cleaning the pipette and repeating the operation. Care must also be taken not to draw in air with the blood or with the diluting fluid. If any air should be drawn in it is well to at once draw in diluting fluid to prevent the blood clotting in the pipette as it is difficult to remove clotted blood. With the blood thoroughly mixed with the diluting fluid it is not necessary to make the count at once. If the pipette is kept in a horizontal position it may be carried some distance. It is better to make the count as soon as possible, though the blood will keep for several hours unchanged in the diluting fluid.

Filling the counting chamber. When ready to fill the counting chamber, the pipette should be shaken and rotated to get an even distribution of the corpuscles. One minute will usually be found sufficient for this. The diluting fluid in the long arm of the pipette is then expelled by compressing the rubber tube and twisting it.

One should never blow in the tube as that would be apt to cause saliva to mix with the diluted blood. After a few drops have been expelled a medium sized drop, obtained by simply compressing the rubber tube, is placed on the center of the counting chamber and the cover glass adjusted. In placing the cover glass care must be taken to avoid including air bubbles. If one side of the cover is placed in position and the other gradually lowered there will be no danger of including air bubbles. The cover glass should be placed as quickly as possible. A delay will result in an uneven distribution of the red corpuscles, the surface of the drop before being covered being rounded the corpuscles fall on the ruled disc from unequal thicknesses of fluid. The drop should be large enough to fill or very nearly fill the central disc without running into the trench or between the cover glass and the plate. The proper size of the drop must be learned by experience. With a little practice one can get the proper sized drop at the first trial. If the cover glass fits closely a play of colors (Newton's rings) will be seen between the cover glass and the plate. If they are not seen it is because the cover glass is not in place. The layer of blood is consequently more than 0.1 mm. in thickness. Gentle pressure on the corners of the cover glass may facilitate the appearance of the colors, but they must remain after the pressure is removed. The counting chamber and cover glass should be cleaned and another drop adjusted if the fluid runs into the trench or between the cover glass and the plate, if the disc is not well filled with fluid, if air bubbles are included, if the interference colors (Newton's rings) are not seen, or if the blood is found to be unevenly distributed. Time is saved by brushing off dust or lint from both counting chamber and cover glass with a small camel's hair brush before filling the counting chamber.

Counting. The counting chamber should be kept level after the drop of blood is placed in it. The count is made on a microscope with a level stage. It is convenient to use a x 4 (2 inch) ocular and a five mm. (^ in.) objective or a special four mm. (|^ in.) objective with a long working distance, N. A. 66. After the counting chamber is placed on the stage one must wait until the corpuscles have settled on the lines. Count the corpuscles in one hundred squares. It is well to count blocks of 25 squares in each corner of the ruled space. Clean the counting chamber and cover glass, place another drop and count the corpuscles in another 100 squares. The pipette should be shaken for a minute and a few drops expelled before placing the second drop in the counting chamber. If the two counts do not agree closely count another 100 squares in another drop.

Computation. Divide the number of corpuscles counted by the number of squares counted, divide this by the dilution and multiply this quotient by 4000 as each square represents ^^oVo of a cubic millimeter of blood. The result will be the number of corpuscles per cubic millimeter.

No. Corpuscles counted x dilution x 4000 No. of corpuscles per r No. of squares cmm.

For example suppose 1321 corpuscles were counted in 200 squares with blood diluted .5:100. The computation would be:

= 5284000

The blood examined has 5,284,000 red corpuscles per cmm.

Limit of error. Using such a high dilution and such a small quantity of blood the error is at best rather high. Thoma and Lyon obtained an error of five per cent, in counting 200 corpuscles, two per cent, with 1250 corpuscles and one-half per cent, with 20,000 corpuscles. A variation of 100,000 corpuscles is not ordinarily important. This is close enough for clinical purposes.

Cleaning the apparatus. It is important to clean the apparatus as soon as the counts are made. If blood dries in the pipette it may take several hours to remove, while if cleaned promptly, it requires only two or three minutes. The counting chamber is to be cleaned with pure water only. , As the plate and disc are cemented to the slide by Canada balsam, alcohol or anything that will act on balsam must not be used. The cover glass may be cleaned with water, then with alcohol. For drying the counting chamber and cover glass about the best thing is a linen handkerchief that is practically worn out. A new one is too harsh. Japanese lens paper may be used but it is not so convenient as soft linen. Anything more harsh than lens paper or old soft linen should not be used. The pipette should be cleaned, after expelling the remaining diluted blood, with pure water, drawing in water and expelling it several times, then with alcohol, then with ether, finally forcing air through until it is thoroughly dry. When the pipette is drj'- the glass bead will roll about freely in the bulb without adhering to any part. An aspirating bulb will be found time saving in cleaning the pipette. To draw fluid into the pipette the rubber tube may be attached or the aspirating bulb may be compressed and the thumb placed over the valve. Care must be taken not to allow the aspirator to become moistened during cleaning as the last step is to force dry air through the pipette. Even when care is taken to clean the pipette well it will be found necessary at more or less long intervals to fill with strong nitric acid and let it act for several minutes. All trace of the acid must be removed by drawing water through the pipette several times, following the water with alcohol^ ether and dry air as ordinarily.

COUNTING THE LEUCOCTYES

If the counting chamber with the Zappert-Ewing ruling is used the leucocytes may be counted in the same preparation as the red corpuscles. The leucocytes in the entire ruled space, nine sq. mm., are counted. The leucocytes are readily distinguished as they have a bluish tinge in contrast to the straw color of the red corpuscles. A dilution of 1:100 is more accurate when the leucocytes are to be counted. Repeat the count with a second drop as with the red corpuscles.

Computation. As with the red corpuscles divide the number of leucocytes counted by the volume of blood counted (.9 cmm.), and this by the dilution. The count should be repeated with a second drop. The formula for leucocytes counted with a dilution of 1:100 is:

No. of leucocytes counted x 10 x 100

T = No. of leucocytes per cmm.

When the counting chamber having only the central square millimeter ruled is used, a pipette giving a dilution of 1 :10 should be used. As it costs more to get the two pipettes and is less convenient to use it is recommended to get the counting chamber with the Zappert-Ewing ruling.

With the special pipette for leucocytes it is necessary to have

COUNTING THE BLOOD PLATES 9

a larger drop of blood than for the red corpuscles. As the fluid will run out of this larger pipette it is necessary to keep it as nearly horizontal as possible. Acetic acid one per cent, (glacial one-third per cent.) is preferable as the diluting fluid. With this fluid the red corpuscles are made transparent, the nuclei of the leucocytes standing out in bold relief. With a dilution of one part of blood to ten of the acetic acid it is necessary to mix the blood and diluting fluid quickly; otherwise the leucocytes will be found in clumps, making an accurate count impossible. The method of adjusting the drop in the counting chamber is the same as for counting red corpuscles. The leucocytes in the entire ruled area of the Thoma's counting chamber, 400 squares, should be counted. In computing the results multiply the number of leucocytes counted by 10, since the 400 squares represents .1 cmm. of diluted blood, and multiply this product by 10, if the dilution was 1:10, to give the number in undiluted blood.

COUNTING THE BLOOD PLATES

The blood plates show a marked tendency to undergo dissolution soon after the blood is taken from the blood vessels and to adhere to each other and to foreign substances. Special precautions must be taken in enumerating them. Several methods have been used, three of which are given in detail.

Pratt^s method. Pratt used the following diluting fluid, which keeps indefinitely unless moulds or bacteria develop :

Sodium metaphosphate (Merck) 2 grams

Sodium chloride 0.9 gm.

Distilled water 100 cc.

The number of erythrocytes is determined in the usual manner with the Thoma hematocytometer. A few cubic centimeters of the diluting fluid are placed in a watch glass. All the glassware used must be perfectly clean. Blood is obtained from a puncture free enough to allow the blood to flow freely. A sterilized platinum loop, as used in bacteriological work, with a diameter of about three mm. is filled with diluting fluid and the center of the loop brought in contact with a fresh drop of blood. There should be three or more parts of fluid to one of blood. A portion of the mixture is at once placed on a slide and covered with a cover glass.

The diluted blood should spread so that the erythrocytes are well separated. It is not necessary to mix the blood and diluting fluid by long stirring. Two preparations should always be made. If the count varies much in the two, other preparations should be made. Examination is made with an oil immersion objective. A square diaphragm in the ocular, easily made of stiff paper, facilitates counting. Both the blood plates and erythrocytes are counted in fields taken at random in different parts of the specimen until 250 to 500 erythrocytes have been seen. This will give the ratio of plates to erythrocytes. The number per cmm. is obtained by multiplying the number of erythrocytes per cmm. by this ratio. Kemp and Calhoun's method.— Kemp and Calhoun used the following diluting and fixing fluid:

Formalin (40%) 10 cc.

Sodium chloride (1% aq. soln.) 150 cc.

(Color with methyl green or methyl violet if desired) .

In this method the blood comes in contact with the fixing fluid before touching anything else. The site of puncture is carefully cleaned and dried. Puncture is made, the first drop wiped off and diluting fluid placed on the site of puncture so that the next drop as it emerges flows into the diluting fluid. Mix thoroughly for a few seconds with a clean glass rod then transfer a large drop with the glass rod to the Thoma counting chamber and cover with a thin cover glass. If the corpuscles are fairly evenly distributed, let the chamber rest quietly for about five minutes. Count the red corpuscles and blood plates in about six frames of 16 squares each. This usually gives about 100 blood plates. With a small number of blood plates or with not so even a distribution more than six frames should be counted. The number per cmm. is obtained by multiplying the number of erythrocytes, obtained in the usual manner, by the ratio of blood plates to erythrocytes.

Wright and Kinnicutfs Method.— The diluting fluid is composed of two parts of an aqueous solution of ''brilliant cresyl blue '^ (1 :300) and three parts of an aqueous solution of potassium cyanid (1:1400). These two solutions must be kept in separate bottles and mixed and filtered immediately before using.

The blood is diluted 1:100. The process should be done as rapidly as possible. Count in the ordinary counting chamber, using a high power dry objective. The authors used the thin

ESTIMATION OF HEMOGLOBIN cover glass of Zeiss with the central excavation. After the counting chamber is filled, it is let stand 10-15 minutes to let the platelets settle. The red corpuscles are decolorized and appear as ''shadows." The nuclei of leucocytes are stained dark blue. The platelets appear as sharply outlined round or oval or elongated lilac colored bodies.