BIOTIC STRUCTURE AND BIOTIC ENERGY 13 



colloid becomes amenable to a stimulus thrown in from without, 

 or, passing this, to a point at which without any outside stimulus it 

 becomes sufficiently charged with chemical products to show spon- 

 taneous irritability and discharge automatically. Here we observe 

 at each beat a sudden chemical reversal followed by a slow period 

 of recovery on the part of the colloid, just as in the heated gelatine 

 solution there is a disruption at the higher temperature followed on- 

 cooling by a slow return to the original condition of combination. 



A similar sequence of phenomena occurs in nearly all forms of 

 living matter, and the periodicity can be altered, diminished, or 

 made more evident by stimuli from without of physical, chemical, 

 or physiological nature, or by altering in varying ways the crys- 

 talloidal ions in union with the protein. Take, for example, the 

 induction of rhythmic activity in skeletal muscle, demonstrated by 

 Biederman and by Sidney Ringer as a result of artificial ionic 

 variation, and its quiescence by dipping in solutions containing the 

 antagonistic ions. 



But apart from external stimulation, phasic activity in some 

 degree or other is inherent in the cry stallo- colloids of all living 

 matter. We see it demonstrated in the unstriated muscle of all parts 

 of the body viz., alimentary canal, bladder, uterus, spleen, arterial 

 walls, everywhere in fact and with varying rhythm in varying 

 situations according to development and requisite physiological 

 function. It is seen also in the rhythmical discharges of the 

 central nervous system, we have noted its presence already in the 

 regulation of respiration, and further characteristic examples are 

 seen in Cheyne-Stokes breathing, in the Traube-Hering curves, and 

 as demonstrated by S chafer in every discharge of a voluntary 

 character from the motor cells of the cord out to the skeletal muscles, 

 showing here a rhythm of ten to twelve cycles per second. 



The same periodicity is observable, but with much slower 

 periods, in the case of all the secreting glands ; there is in each case 

 a period of resting and accumulation of material, followed by a 

 period of discharge. Exhaustion follows efficient discharge, and a 

 period of refractoriness to stimulation supervenes before another 

 discharge can occur. 



The gland discharge may also be precipitated by stimulation 

 from without at certain points in the cycle, but in the absence of 

 the external and usual stimulus the potential of the cell tending 

 towards discharge gradually rises with accumulation and corre- 



