32 POPULAR SCIENCE MONTHLY. 



ready to our hands, who can say what further discoveries will not 

 shortly be made, even in such well-worked fields as chemistry and 

 physics ? 



The mention of physical chemistry brings me to what I may term 

 the second head of my discourse, the second striking characteristic of 

 modern chemical physiology: this is the increasing importance which 

 physiologists recognize in a study of inorganic chemistry. The materials 

 of which our bodies are composed are mainly organic compounds, 

 among which the proteids stand out as preeminently important; but 

 every one knows there are many substances of the mineral or inorganic 

 kingdom present in addition. I need hardly mention the importance 

 of water, of the oxygen of the air, and of salts like sodium chloride 

 and calcium phosphate. 



The new branch of inorganic chemistry called physical chemistry 

 has given us entirely new ideas of the nature of solutions, and the fact 

 that electrolytes in solution are broken up into their constituent ions 

 is one of fundamental importance. One of the many physiological 

 aspects of this subject is seen in a study of the action of mineral salts 

 in solution on living organisms and parts of organisms. Many years 

 ago Dr. Einger showed that contractile tissues (heart, cilia, etc.) con- 

 tinue to manifest their activity in certain saline solutions. Howell 

 goes so far as to say, and probably correctly say, that the cause of 

 the rhythmical action of the heart is the presence of these inorganic 

 substances in the blood or lymph which usually bathes it. The subject 

 has more recently been taken up by Loeb and his colleagues at Chicago : 

 they confirm Ringer's original statements, but interpret them now as 

 ionic action. Contractile tissues will not contract in pure solutions of 

 non-electrolytes like sugar or albumin. But different contractile tissues 

 differ in the nature of the ions which are their most favorable stimuli. 

 An optimum salt solution is one in which stimulating ions, like those 

 of sodium, are mixed with a certain small amount of those which like 

 calcium restrain activity. Loeb considers that the ions act because they 

 affect either the physical condition of the colloidal substances (proteid, 

 etc.) in protoplasm or the rapidity of chemical processes. 



Amoeboid movement, ciliary movement, the contraction of muscle, 

 cell division and karyokinesis all fall into the same category as being 

 mainly dependent on the stimulating action of ions. 



Loeb has even gone so far as to consider that the process of fertiliza- 

 tion is mainly ionic action ; he denies that the nuclein of the male cell 

 is essential, but asserts that all it does is to act as the stimulus in the 

 due adjustment of the proportions of the surrounding ions, and sup- 

 ports this view by numerous experiments on ova in which without the 

 presence of spermatozoa he has produced larvae by merely altering the 

 saline constituents and so the osmotic pressure of the fluid that sur- 



