CHAP. xvi. ] PHYSIOLOGICAL OFFICE OF RESPIRATION. 255 



plasmas, certain substances destined afterwards to play more or 

 less important parts in the different functions. Thus it is that 

 we have to speak of excretion and secretion. 



NOTE. 



A litre is about a quart English. A kilogramme is a thousand grammes, 

 j According to the new system of weights and measures introduced into France 

 , at the Revolution, deci as a prefix means tenth ; centi, hundredth ; milli, 

 thousandth, when the principal unit is progressively fractionised : deca as a 

 1 prefix means tenth ; Jiecto, hundredth ; kilo, thousandth, when the principal unit 

 1 is progressively augmented or multiplied. Thus millimetre is the thousandth 

 ; part of a metre; hectogramme a hundred grammes, and so on. In Professor 

 j Roscoe's Lessons in Elementary Chemistry a comparison of the French 

 I metrical with the common measures is given. Translator. 



