56 MANUAL OF PHYSIOLOGY. 



a strictly chemical point of view, does Dot set forth their physio- 

 logical importance or express in any way the relation they bear to 

 the vital phenomena of organisms. 



The following enumeration of the chief chemical ingredients 

 found in the tissues has regard to their physiological dignity as 

 well as to their chemical construction, and will thus it is hoped 

 assist the student to distinguish the different groups, and give him 

 a better idea of their vital relationships, than a more strictly sys- 

 tematic classification. 



A. NITROGENOUS. 



I. Complex bodies forming the active portions of all tis- 

 sues Plasmata. E.g., protoplasm, blood-plasma. 

 II. Bodies entering into the formation of, and which can 

 easily be obtained by analysis of Group I. Albu- 

 mins. E.g., serum-albumin. 



III. Bodies the outcome of differentiation, manufactured 



in the tissues by Group I. Albuminoids. E. g., 

 gelatin, etc. 



IV. Bodies containing nitrogen, being intermediate, bye, 



or effete products of tissue manufacture. E.g., leci- 

 thin, urea, etc. 



B. NON-NITROGENOUS. 



V. Carbohydrates in which the hydrogen and oxygen ex- 

 ist in the proportion found in water. E.g., starch 

 and sugar. 

 VI. Hydrocarbons containing oxygen in less proportions 



than the above. E.g., fats. 

 VII. Salts. 

 VIII. Water. 



CLASS A. NITROGENOUS. 

 Group I. PLASMATA. 



Under this group may be placed a great variety of materials 

 which must be acknowledged to exist in the living tissues as ex- 

 alted chemical compounds, of whose chemical constitution, how- 



