GENERAL CONSIDERATIONS. 255 



assimilation of its nutritive constituents by the tissues, it is 

 necessary to keep it up to the proper nutritive standard ; and 

 this is effected by alimentation, digestion, and absorption. 

 Fifth, we have certain secretions, necessary to the above- 

 mentioned processes ; and the products of physiological waste 

 or decay of the tissues are removed by excretion. Sixth, the 

 processes of vegetative life involve the production of heat, 

 and are regulated and coordinated by the nervous system. 



The second class of functions relates to animal life, and 

 these are called the functions of relation. In this class, are 

 included movements, voice and speech, the functions of the 

 cerebro-spinal nervous system, and the operation of the spe- 

 cial senses. 



In studying the processes of nutrition of the general sys- 

 tem, we observe that certain constituents of the organism, 

 which contain nitrogen and are exclusively of organic origin, 

 have the property, in the living body, of self -regeneration ; 

 i. e., when these parts are brought in contact with nutritive 

 matter in proper form, as it exists in the blood, this matter 

 is appropriated and transformed into the substance of each 

 tissue and organ. It is in this way that, during adult life, 

 the different parts of the organism are maintained in a tolera- 

 bly uniform condition. In the absence of an exact knowledge 

 of the cause and nature of these assimilative processes, we call 

 them vital ; which term is applied to a constant property of liv- 

 ing, organized parts. Physiologists have ascertained that each 

 tissue and organ of the body possesses one or more character- 

 istic organic nitrogenized constituents which are possessed of 

 this so-called vital property. But, at the same time, it is al- 

 ways observed that the organic nitrogenized constituents of 

 the organism are combined most intimately with a tolerably- 

 definite quantity of inorganic matter, which latter regulates, 

 to a certain extent, the nutritive processes, and constitutes, 

 also, an important component part of the tissues. It is ob- 

 served, in addition, that, during early life, when the system is 

 proceeding toward its perfect development by growth, the 

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