AND PHYSIOLOGY. 



9 



17. Immediate Principles Physiologically Grouped. — - 

 If we group the preceding substances according to their phy- 

 siological relations, we might, with Dr. Carpenter, bring them 

 all into four divisions. 



1. Histogenetic Substances, or such as are converted into 

 animal substances, and are nitrogenous. 



2. Calorific Substances, mainly intended to produce heat, 

 and are non-nitrogenous, as, sugar and oils. 



3. The components of the living animal substance. 



4. Excrement it ions Substances, formed within the body, 

 and thrown out of it. 



18. Other Probable Principles.— Quite a number of other 

 substances have been detected in the human system, which 

 some regard as immediate principles. But it is safer to wait 

 till further examination has removed doubt. 



19. Several of the above principles are capable of crystal- 

 lization, and are some- 

 times found in that state fiq. i. 



in the body. Figs. 1 

 and 2 show two exam- 

 ples of these crystals, 

 the first of Hippuric 

 acid, and the other of 

 Creatine. 



20. To go into minute 

 details respecting the im- 

 mediate principles above 

 described, would occupy 

 too much space in a work 

 like the present. But a 

 few statements respect- 

 ing the most import- 



17. What are the Groups of these substances when physiologically grouped ? Who \» 

 the authority for this? Define the Histogenetic and the Calorific group. What are ex- 

 creinentitious substances ? Are there anyvother principles in the body ? 



1* 



