CHAPTER VII 



SYMBIOLOGY— THE BIOLOGICAL RELATIONSHIPS OF 

 ORGANISMS 



I. GENERAL INTRODUCTION 



Symbiology is the science which treats of the biological relationship of 

 living organisms, animal and vegetable. A general discussion of the 

 subject is essential to a clearer comprehension of the science of 

 bacteriology or microbiology. It will be found that in the treatment of 

 bacteria in disease we are dealing solely with symbiotic relationships. 

 The term symbiosis has been variously interpreted and misapplied. 

 The most common mistake is to define the word as a mutually advan- 

 tageous biological or physiological association of two or more organisms. 

 Some confuse symbiosis with commensalism. By commensalism is 

 meant the living together of two or more parasitic organisms upon a 

 common host, and is therefore 'a form of compound symbiosis. In 

 this case the common (commensal) parasites apparently bear no harmful 

 relationship to each other, and may and often do bear a mutualistic 

 relationship toward each other. 



Symbiology in the broader sense, therefore, means the science which 

 treats of parasitology, of symbioses in the narrower sense, of commensal- 

 ism as above defined, of paracytosis, of patrocytosis, of leucocytosis, and 

 of all other forms of intimate physiological and pathological associations 

 of living things. The subject, in the broader and more comprehensive 

 sense, has not received the consideration which it deserves, although some 

 of the special phases have been very f uUy treated, as for example general 

 parasitology and leucocytosis. Nothing more can be done than to outline 

 the subject and to suggest that any special discussion or fuUer treatment 

 be looked up in some of the excellent recent monographs (example — 

 Herms, William B. Medical and Veterinary Entomology. The MacMil- 

 lan Company, 1915). 



A statement of cytology and of embryology is essential to the better 

 understanding of symbiology and the related sciences adenology and 

 bacteriology. The following is a brief summary of the subject. 



Van Leeuwenhoek, Hooke and Malphigi (about 1660) are usually 

 credited with having made the first observations regarding a cellular 

 structure in plants. The first published illustrations of plant cells per- 



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