NUTRITION. 95 



life, if retained in any considerable quantity. Here, also, are 

 formed the secretions destined to serve the animal in the per- 

 formance of the digestive and other functions ; in the animal 

 forms mostly by specialized cells acting vicariously for the 

 other tissues of the body. These are special developments of 

 function, seen as we ascend the scale of life. But these func- 

 tions are also present in the unicellular forms of life, where 

 there is no such division of labor or function developed. It 

 is not a new function, but a special development of cells to 

 act in this matter for the whole. 



