2 IMMEDIATE PRINCIPLES 



constituents of the tissues of plants are albuminous bodies, 

 and carbonic hydrates; for these exist in all plants. The 

 characteristic property of a plant is its power of forming 

 its tissues out of inorganic materials. 



The term protoplasm is used to denote the apparently, 

 but not really, homogeneous substance which forms the 

 active parts of the tissues of plants and animals. It con- 

 sists chiefly of albuminous bodies, and exhibits in itself all 

 the essential phenomena of life : for in it, not only the 

 general actions which belong to the organism as a whole, 

 but the specific actions of particular parts, such as those of 

 muscle, nerve and gland, have their seat. 



IMMEDIATE PRINCIPLES OF FOOD. 



* ^ The term " immediate principle" or " proximate principle" (<rrot%stav) is 

 applied to any ' ' substance, " in the chemical sense, which exists as snch in 

 living organisms. It is tmderstood to be applicable to bodies which are met with 

 in the secreted liquids, as well as to the constituents of the blood and tissues. 



ALBUMINOUS BODIES (PROTEIDS). 



Proteids are non-crystallizable bodies of unknown constitution, of which 

 the centesimal composition is about Carbon 53, Hydrogen 7*5, Nitrogen 

 1 5 '5, Oxygen 23, Sulphur I *o. They are soluble, or capable of imbibition 

 with water, insoluble in alcohol or ether. They are all stained yellow by 

 nitric acid, and then disintegrated, leaving a yellow precipitate which dissolves 

 orange red in ammonia. 



Aqueous solutions of proteids are Isevo-rotatory. When a solution is sepa- 

 rated from water by a septum of colloid membrane, the proteid diffuses with 

 extreme slowness into the water. 



They occur in the tissues or fluids of plants and animals under two prin- 

 cipal forms, distinguished from each other according as they are coagulated or 

 remain in solution when boiled. 



The coagulable proteids comprise the albumins proper, which are soluble in 

 water, and the globulins, which are insoluble, but are readily held in solution 

 in presence of neutral salts, particularly NaCl. From these (often called 

 native albumins) the mass of the proteid material of animal and vegetable 

 tissues is formed, 



The albuminatcs are soluble in aqueous liquids, only when these are acid 

 or alkaline : they are precipitated by neutralization. They must be regarded 

 as derivates from the others ; for bodies which correspond entirely in their 

 characters with those albuminates which exist in the tissues of plants and 

 animals can be obtained by the prolonged action of alkalies or acids on 

 coagulable proteids. 



