2l6 



PRINCIPLES OP GENERAL PHYSIOLOGY 



added ; the systolic arrest appears immediately. It is to be noted that the amount of calcium 

 added is only just about the amount required to neutralise the potassium present in the 

 solution, so that the effect is not due to the calcium but to the digitoxin, which had been 

 in abeyance until the calcium was added. 



Hamburger (1910) finds that calcium increases the amoeboid movement of 

 phagocytic leucocytes, while barium, strontium and magnesium have no such 

 effect. 



Chiari and Januschke (1910) describe a remarkable action of calcium. If 

 sodium iodide is injected intravenously into dogs, fluid is exuded into the pleura 

 and pericardium, and redenia of the lungs is produced. But, if calcium chloride is 

 injected simultaneously, these cavities remain quite dry. Exudation produced in 

 other ways is also subject to the same effect of calcium. Inflammation and 

 swelling of the eyelids, caused by oil of mustard, is prevented by previous sub- 

 cutaneous injection of calcium chloride. The action appears to be on the 



FIG. 66. INACTIVITY OF DIUITOXIN ON THE FROG'S HEART IN- ABSENCE OK CAM 11 \i 



(Clark, 1912, fig. 7; Proc. K. Soc. Ml.) 



permeability of the walls of the blood vessels, increasing the " consistency " of the 

 colloidal systems of the cell membranes. 



An interesting fact noted by Mines is that strontium can be a>itayoni#e,d by calcium in 

 respect to its action on the heart muscle. The characteristic tonic effect of calcium 

 is possessed to a greater degree by strontium ; but, if to a Ringer's solution, containing 

 sufficient strontium to give a marked prolongation of the beat, there be added the normal 

 amount of calcium salt, the beat returns to its correct form. It is difficult to say in what 

 way this effect is produced ; possibly calcium lowers some form of surface energy to a greater 

 extent than strontium does, and therefore displaces it from the cell membrane, or calcium may 

 give up its electrical charge with greater ease than strontium does, and thus maintain the 

 proper colloidal consistency of the membrane. 



In the absence of calcium, the heart of the frog is unable to give contractions. 

 The continuance of the electrical change shows that the excitatory process goes on 

 (see Mines, 1913, 3, p. 231), and Locke and Rosenheim (1907) found that glucose 

 is still consumed. It appears that there is some break in the mechanism of 

 conversion of chemical energy to contractile stress. The state of the active 

 surfaces (see below, page 448), in the absence of calcium, is such that the 



