TRANSACTIONS OP SECTION I. 689 



The Liquid Pressure theory was worked out in consequence of a similar 

 theory on the ascent of sap in plants. It was shown that, with the recognition 

 of a new semipermeable membrane, impermeable to liquids but permeable to 

 gases — the ' aeropermeable membrane ' — the force of liquid pressure became 

 available as a source of power. The force of liquid pressure under ordinary 

 conditions is nullified by cohesion; but it has great magnitudes, being about 

 20,000 atmospheres per gramme for water at low temperatures. 



According to this theory muscular contraction is caused by the respiration of 

 glycogen through an aeropermeable membrane, according to the general 

 equation : — • 



(CeH,„OJ n +6/1 0, 

 = 6n C0,+5nH,0. 



The liquid pressure which causes the contraction is due to the chemical pro- 

 duction of water. 



Macdougall's cytological observations of the process of contraction in the 

 wing muscles of insects lend support to the view that an increase in the water 

 content of the cells accompanies contraction. And this is also borne out by 

 Maclendon's work on the changes in electrical conductivity of contracting 

 muscles. 



Further, the work of Overton and Meiggs on the osmotic properties of 

 muscle shows that, although the entrance of water causes contraction, yet, 

 while the muscle is still active, water as such cannot enter the cells. Hence the 

 presence of an aeropermeable membrane has already been experimentally demon- 

 strated in muscle. This is confirmed by Fletcher's work on fatigued muscles. 



The reaction is to be regarded as a ' floating ' respiration superimposed upon 

 the normal respiration of the cells, analogous to the carbohydrate respiration 

 observed by F. F. Blackman in leaves. The function of nervous or electric 

 excitation is that of a stimulus which liberates some essential part of the 

 reacting complex. 



The physics of liquids has not been sufficiently worked out to enable an 

 exact calculation of the energy balance of the reaction to be made. But at least 

 forty-five per cent, of the chemical energy evolved during respiration may be 

 directly converted into liquid pressure by means of the aeropermeable mem- 

 brane. Broca's ' travail physiologique ' is in fact liquid pressure, and the name 

 is not inapt, for the use of this form of energy is at present confined to living 

 organiisms. 



The relaxation of muscles is explained as being due to the re-evaporation of 

 water through the membrane. This process requires heat, and would absorb 

 nine per cent, of the total energy of the respiration reaction, thus serving to 

 reduce the excessive heat evolved. 



5. The Elasticity of the Strophanthinised Heart. 

 By Dr. J. Tait and Dr. Harold Pringle. 



SUBSECTION OF PSYCHOLOGY. 



WEDNESDAY, SEPTEMBER 8. 

 The following Papers were read : — 



1. Behaviourism. By Arthur Robinson, M.A., D.C.L. 



Behaviourism is the view that ' consciousness is behaviour,' and that psycho 

 logy is ' the science of behaviour.' It appears to have originated partly from a 

 desire to make the subject-matter of psychology more ' objective ' by limiting it 



1915. Y Y 



