V. INFLUENCE OF IONS ON THE 

 OEGANISM 



ALL living substances consist of crystalloidal and 

 colloidal material. The colloids are compounds 

 based upon a nucleus of carbon, " the asymmetrical 

 carbon atom," which, from its having four poles of 

 attraction or valencies, is eminently qualified to 

 form the inner skeleton of complex combinations. 



The crystalloidal substances are well known to 

 chemistry. They obey the ordinary laws of the 

 science ; and their absorption and excretion by 

 living organisms is governed by the laws of osmosis 

 and diffusion. They are divisible into the two 

 groups of electrolytes and non-electrolytes ; the 

 former consisting of the salts, acids, and bases ; the 

 latter mostly of organic substances such as sugar 

 and urea. Their molecular weight is low, they have 

 a great affinity for water, and readily pass through 

 animal membranes. They perform important duties 

 in the organism by their physico-mechanical and 

 physico-chemical properties. They influence many 

 of the organic processes, impart a stimulus to various 

 functions, and take an active share in metabolism. 

 However, "it is not the salts, but the ions of the 

 salts, which are essential to the organism."* There 



* Pauli's " Physical Chemistry in the Service of Medicine," 

 p. 16. 



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