FART I. 



GENERAL HISTOLOGY. 



PART I. Living Matter in Health and Disease. 



I. THE NATURE OF LIFE. 



Physicians deal chiefly with life. It is true that the materi- 

 als of human or other organized bodies are the same as those 

 of the inorganic world, and the knowledge of physics and 

 chemistry cannot be dispensed with, but our patients are liv- 

 ing beings. The functions of their bodies are vital functions, 

 not known outside the living world. Physiological activities, 

 as well as psychological, depend on life. Pathological changes 

 are modifications of vital actions. The activities we seek to 

 modify by therapeutics are mostly vital activities. Hence the 

 need of studying biology, or the science of life. The mys- 

 tery of life is no reason for avoiding its study. It is no more 

 mysterious than any other ultimate fact in nature. 



Only two theories possible to account for the nature of 

 things. One is called Monism, and regards the universe as a 

 mechanical evolution of a single substance, which is generally 

 considered to consist of material atoms, very minute and inde- 

 structible, with spontaneous motion. Some, however, teach 

 that immaterial force is the only substance. The other theory 

 is called Dualism, because it admits two kinds of substance, 

 one atomic material and mechanical, and the other spiritual 

 and invisible, but both capable of acting upon each other. 

 Under one of these modes of thought we must range our- 

 selves if we think at all. Many physiologists have tried to de- 

 fine life so as to avoid both theories and have been amusingly 

 unsuccessful. 



Bichat defined life as "the sum of the functions by which 

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