Protozoölogy

Front matter

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Preface

Ir is my purpose, in the present volume, to discuss some of the old and some of the new problems in biology as illustrated by the lowest forms of animal life, the protozoa, the subject matter being founded on a course of Lowell Institute lectures given in the fall and winter of 1907. Interest in these organisms, of late, has centred mainly in the practical side until, to many biologists and to most medical men, protozodlogy implies the science dealing with pathogenic protozoa. Protozodlogy has a broader scope than this, and it is one purpose of this book to check, if possible, the limiting tendency and to point out again the important part that the protozoa play in the problems of modern biology. ‘This is the more necessary because, in my opinion, in the application of biological principles which underlie the vital phenomena of free and parasitic forms alike, will be found the most valuable data for the more practical sides of protozodlogy. Here in these mere specks of animated jelly, which rarely measure more than the hundredth part of an inch, we find, in their simplest forms, the manifold processes of the living organism. Digestion and assimilation; respiration, with its dual action of oxidation and renewal; excretion and secretion; irritability and fatigue; reproduction, together with the unfathomed mystery of fertilization and inheritance, all find expression in these simple animals and raise the lowest protozoén immeasurably above the most complex of non-living substances. With such vital processes reduced to their lowest terms in these protozoa, we should expect to find a wealth of material for the study of life phenomena which in the higher animals are masked under a cloak of differentiated structures, and the study of these more general functions should form the basis for explanations or interpretations of the more specialized adaptations which are characteristic of pathogenic forms. This more comprehensive field, as I understand it, is the scope of modern protozoélogy.

The researches of Louis Pasteur, in connection with fermentation, souring of wine, and the silkworm disease, led him to many reflections and conclusions as to the nature of various contagious and hereditary diseases. Perhaps more than any other single research, his investigations, begun in 1865, on the cause and ‘prevention of silkworm epidemics (to which De Quatrefages had given the name of pébrine, iv PREFACE because of the characteristic black spots), led him to the belief that many hutnan ills are similarly due to minute and microscopic forms of life, and so paved the way for the later generalization which now dominates medicine—the germ theory of disease. Ahead of his times in recognizing the present-day axiom that epidemics are ended by prevention rather than by individual treatment, Pasteur patiently advised and demonstrated, in connection with the silk industry, that perfect silkworms and moths would not develop from eggs having pébrine corpuscles on them. It is of no importance that these corpuscles were not recognized by him as the spores of a protozoén, but the important results which followed their discovery, and which led to increased length of human life, and to the mitigation of human and of animal suffering throughout the civilized world, make an increasingly substantial monument to the patience, courage, and virility of this man of pure science, who, by the apotheosis of scientific method, proved these unknown corpuscles to be the cause of this silkworm disease.

The recently opened chapter of the protozoan diseases of man might have been earlier studied had these observations of Pasteur upon the spores of Nosema bombycis been followed up. The parasitic protozoa were known and the free-living forms had been brought into prominence in scientific circles through the controversies over the cell theory and the theory of spontaneous generation, but more than thirty years were to elapse before general acceptance of the first human disease attributable to protozoa.

The other minute organisms, bacteria and yeasts, whose presence Pasteur had demonstrated in his experiments on fermentation and spontaneous generation, were not neglected. In the hands of R. Koch the means of studying bacteria were perfected, and “culture” methods were introduced which soon raised bacterial research to the dignity of an independent branch of biological science. The ease with which bacteria could be studied, thanks to these methods, and the rapidly increasing list of bacterial diseases, seemed to divert the attention of specialists from the pursuit of protozoan diseases and to confine it to research on those of bacterial origin. Attempts were repeatedly made, however, to cultivate protozoa as the bacteria are cultivated, on artificial media, but until the present decade such efforts, for the most part, were fruitless. The difficulties in applying the artificial culture method to the protozoa are due, essentially, to the differences in their mode of nutrition. Some of them, indeed, are similar to the bacteria in being saprophytic or saprozoic (to use Blanchard’s expressive term), absorbing liquid or dissolved proteid matter through the body wall. Such forms lend themselves to the culture method, and the success of Novy and MacNeal and others with trypanosomes, herpetomonads, etc., in artificial liquid media follows from this nutritional characteristic. Other forms of protozoa, as, for example, the parasitic amebee, may or

PREFACE = may not lend themselves to the culture method, and then only upon the condition of having other living things as food. Many observers have found that intestinal amebz, and others that feed on bacteria, will thrive on solid culture media provided the latter are seeded with bacteria, and this fact is of the greatest importance in obtaining material for study. Other amebze cannot be cultivated in this way, and it is quite probable, as Liihe maintains, that many parasitic protozoa, especially the intracellular parasites, such as the coccidia, will never be successfully cultivated.

There is need, furthermore, of caution in studying protozoa under such artificial conditions, for they are extremely sensitive to variations and are readily adapted to new conditions. The reactions, both morphological and physiological, of protozoa under such conditions of study require careful control.

The study of protozoa, therefore, even when it is possible to apply bacteriological methods, is fundamentally different from the study of bacteria as at present carried on. The latter, dependent upon growth conditions, colony formation, reactions to media, etc., are essentially physiological and based upon the functions of the organisms. The study of protozoa, on the other hand, is essentially morphological, or based upon the structures of the protozoan cell, and involves the changes in cell structures which an individual undergoes during various phases of vitality. Hence it becomes necessary, first of all, to know the life history of the protozoén and the fundamental modifications which its protoplasm assumes. Modern protozodlogy, therefore, has demanded as a basis for genera and species of protozoa a knowledge of the complete life cycle, and as a basis for classification not the structures of the single cells, but the structures which the protoplasm may assume throughout its entire life history from fertilization to death or until the next fertilization.

The present volume, finally, does not aim at being an exhaustive treatise on the protozoa; it aims, rather, to give an introduction to the study of modern protozodlogy as seen from the author’s point of view; and for numerous omissions, incomplete references, etc., he can only plead the excuse of a large subject crowded into a limited space.

G. N. C.

New York, 1909

Chapter I. General Organization Of The Protozoa

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B. Organs of Locomotion and Glesiftetion EAE See the ce ee A a 2 Pay Pseudopodia and Classification of the Sarcodinga. . . . . .) . 85 Flagella and Classification of the Mastigophora . . . . . . . 42 Cilia and Classification of the Infusoria . . . . . . . . . 49 Parasites and Classification of the Sporozoa . . . . . . . O56

Chapter II. Physiological Activities Of The Protozoa

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Chapter III. Protoplasmic Age Of Protozoa

OBL ARS orgie es ee eee a ae acai tn viii CONTENTS

Chapter IV. Conjugation, Maturation, And Fertilization

Fertilization by Autogamy Fertilization by Endogamy Fertilization by Exogamy Parthenogenesis : Maturation in Protozoa Significance of Conjugation

Chapter V. Parasitism

Structural Modifications and Mode of Life of Protozoan Parasites .

Endogenous Cycle ;

Exogenous Cycle and its Veracca Sporulation in Gregarines

Sporulation in Coccidia

Sporulation in Myxosporidia . : Exogenous Life of Protozoan Parasites .

Air-borne Protozoa an

Transmission by Inheritance . : Transmission by Intermediate Hosts : Effects of Protozoan Parasites on Their Hosts Protozoa and the Cancer Problem

Chapter VI. The Pathogenic Flagellates

The Genus Spirocheta and its Allies .

Spirocheta Balbianii

The So-called Flagella of Spirochetes The Spirochete Nucleus He: Division of Spirochetes

Form Changes and Life Econ

Are Spirochetes Protozoa or Bacteria? .

Chapter VII. The Pathogenic Flagellates (continued)

The Genera Herpetomonas and Crithidia Herpetomonas Donovani and Kala Azar The Genus Crithidia

139 146 150 161 164 171

233 238 241

CONTENTS ix

Chapter VIII. The Pathogenic Flagellates (continued)

The Genus Trypanosoma . . ow (oe eee at mcd TM Sae Se dy Ae mE a oe © The Motile Apparatus of ficypanosoren bi Be, GAP” Fon al Gay exe os Ui The Trypanosome Nuclei Pe ee ten ee eee eh tay, ee ee AOD Form Changes of Trypanosomes. . . . . .. .. . . . . 257 Reproduction of Trypanosomes . . . . . . . . . . . . . 260 Agglomeration. . Nhe Aa in Ba ae Re ee ek cae wee Pea | Invertebrate Hosts Si Tite Gyele be eae A Ge On emere oe tel The Effects of Trypanosomes upon Neriobente Hosts Be ich coe PBS oth wee PARTE

CHAPTER Ix. THE PATHOGENIC HEMOSPORIDIA

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Chapter X. The Pathogenic Rhizopoda

Entameba and the Dysentery Problem. . . . . . . . . . . 294 Rabies and the Negri Bodies in, tis, Hog Ss CN CR ape te ere SATII) Smallpox and the Guarnieri Bodies. 2. . . . . . . 802

Other Protozoan Diseases of Obscure Etiology. . . . . . . . . 811

PROTOZOOLOGY.