COMPOSITION OF THE BLOOD-PLASMA. 21 



principle, a substance extracted from the body, winch cannot be subdivided without 

 chemical decomposition and loss of certain characteristic properties. This definition 

 will apply to all classes of proximate principles, organic as well as inorganic. 



Taking as a basis, the classification proposed by Robin, we may divide the proximate 

 principles of the blood, and, indeed, of the entire organism, as follows : 



1. Inorganic Principles. This class is of inorganic origin, definite chemical compo- 

 sition, and crystallizable. The substances forming it are all introduced from without, 

 and are all discharged from the body in the same form in which they entered. They 

 never exist alone, but are always combined with the organic principles, to form the 

 organized fluids or solids. This union is " atom to atom," and so intimate that they are 

 taken up with the organic elements, as the latter are worn out and become effete, and 

 are discharged from the body, although themselves unchanged. To supply the place of 

 the principles thus thrown off, a fresh quantity is deposited in the process of nutrition. 

 They give to the various organs important properties ; and, although identical with sub- 

 stances in the inorganic world, in the interior of the body, they behave as organic sub- 

 stances. They require no special preparation for absorption, but are soluble and taken 

 in unchanged. They are received into the body in about the same proportion at all 

 periods of life, but their discharge is notably diminished in old age, giving rise to cal- 

 careous incrustations and deposits and a considerable increase in the calcareous matter 

 entering into the composition of the tissues. As examples of this class we may cite 

 water, chloride of sodium, the carbonates, sulphates, phosphates, and other inorganic 

 salts. 



The functions of water in the blood are sufficiently evident. It acts as a solvent for 

 the inorganic salts, the organic salts, and the excrementitious matters. In conjunction 

 with the nitrogenized principles, it constitutes a medium in which the corpuscles are sus- 

 pended without solution. 



The various salts enumerated in the table exist in solution in water and are more or 

 less intimately combined with the coagulable organic principles. Of these, the chloride 

 of sodium is the most abundant. It undoubtedly has an important function in giving 

 density to the plasma and in regulating the processes of endosmosis and exosmosis. In 

 connection with the organic salts and crystallizable excrementitious matters, it may be 

 stated, in general terms, that the blood contains from 14 to 10 parts per 1,000 of matters 

 in actual solution, of which from 6 to 8 parts consist of inorganic salts. The presence of 

 these principles in solution, with the organic coagulable principles, prevents the solution 

 of the corpuscular elements of the blood. The presence of the chlorides and the alka- 

 line sulphates assists in dissolving the sulphates, carbonates, and the calcareous phos- 

 phates. A portion of the carbonates and phosphates are decomposed in the system and 

 furnish bases for certain of the organic salts, such as the lactates, nrates, etc. 



2. Organic Saline Principles. These principles are for the most part formed in the 

 organism, and they exist in the blood in very small quantity. The lactates are probably 

 produced by decomposition of a portion of the bicarbonates and the union of the bases 

 with lactic acid, the lactic acid resulting from a change of a portion of the saccharine 

 matter in the blood. The pneumate of soda is the result of the union of pneumic acid, 

 an acid principle found in the lungs, with the base. The physiological relations of these 

 principles are little understood. The salts formed by the union of fatty acids with bases 

 are probably produced by decomposition of the fatty principles, a great part of which is 

 derived from the food. 



3. Organic Non-nitrogenized Principles. These usually exist in the blood in small 

 quantity and are derived mainly from the food. Lecethine, although it contains nitrogen, 

 is introduced into this class because it presents many of the properties of the fats. It 

 exists in the blood, bile, nervous substance, and the yolk of egg. This principle is sup- 

 posed by Robin to be almost identical with protagon. Its chemical properties and 

 physiological relations are not well understood. The saccharine principles and glyco- 



