[nicholls] medicine AND OTHER NATURAL SCIENCES 9 



i.e., substances that can be dissociated into ions, sucli as acids, alkalis, 

 and their salts, in the economy must be studied in regard to the effects 

 and properties of their positive and negative ions, and, in many cases, 

 of the undissociated molecules existing with them. Non-electrolytes, 

 like urea, ethyl alcohol, and glycerine, produce the effects only of their 

 molecules. These considerations must be taken into account in esti- 

 mating the relative values of certain drugs, for example iodine, 

 bromine, and chlorine in their various salts. Substances applied 

 externally may be driven deeply into the tissues and subsequently 

 absorbed by dissociating them with an appropriate electric current. 



Much of the interchange of matter between the cell and its ex- 

 ternal environment is of the nature of a diffusion or osmosis. It 

 would take us too far afield to discuss this fully, but it may suffice to 

 say that it has been shown that cells are commonly colloidal in nature; 

 their nuclear membranes and ectosarc are what are termed conden- 

 sation membranes, permitting the passage one way or the other, ac- 

 cording to circumstances, of the simpler proteins and various ions, 

 while at the same time conserving the integrity of the cells. Thus, 

 the nature and the rate of metabolic interchange is in large part de- 

 pendent on physical characteristics. 



I spoke shortly ago of equilibrium as a condition which all of the 

 cells of the body attempt to reach. The health of the organism de- 

 pends on maintenance of balance between the various metabolites with- 

 in the cell, between cell and cell, between cell and intercellular sub- 

 stance, between tissue and tissue, and between organ and organ. In 

 fact, growth as well as metabolism comes under this general law. 

 Should the equilibrium be upset while structures are developing we 

 get many forms of aplasia, local over-growths or hypoplasias, mon- 

 strosities, and "cell-rests." Applying the same principle to indi- 

 vidual cells, various degenerations and infiltrations can be explained. 

 Where glandular cells, as for example, in the tubules of the kidney, 

 waste and disappear the interstitial connective tissue is stimulated 

 to excess and proliferates to take their place. Fatty tissues may grow 

 so abundantly that they invade, for example, the muscles, and thus 

 weaken or destroy them. Substances, like sodium urate may be pro- 

 duced in excess, circulate in the blood, and be deposited in bone or 

 cartilage, or in the cells of the kidneys. Perhaps the most striking 

 cases are to be found in certain glands, which are ductless, yet manu- 

 facture an internal secretion, producing its effects by circulation in 

 the blood. These internal secretions are entirely chemical in their 

 nature and effects. The dried gland substance is just as potent as 

 the living gland. Some, even, like adrenin, found in the adrenal 

 gland, can be made artificially. The thyroid gland and the pituitary 



