88 TEXT-BOOK OF PHYSIOLOGY. 



teid, for experiment has shown that the available glycogen is entirely 

 consumed the second or third day. The mechanism by which the 

 energy is liberated, whether by decomposition or direct oxidation, is 

 unknown. The fact that muscle will contract in an atmosphere 

 free of oxygen, that no free oxygen can be obtained from muscle, 

 would support the idea that the mechanism is one of decomposition. 

 Hermann suggests that the energy of a contraction is liberated by 

 the splitting and subsequent re-formation of a complex body belonging 

 neither to the carbohydrates nor fats, but to the proteids to this hypo- 

 thetic body the term inogen is given. This complex molecule, the 

 product of the nutritive activity of the muscle-cell in undergoing 

 decomposition, would yield carbon dioxid, sarcolactic acid, and a 

 proteid residue resembling myosin. On the cessation of the con- 

 traction the muscle-cell recombines the proteid residue with oxygen, 

 carbohydrates, and fats, and again forms the energy-holding com- 

 pound, inogen. The phenomena of rigor mortis support this view. 

 At the moment of this contraction the muscle gives off CO 2 in large 

 amount, develops sarcolactic acid and myosin. There is thus a close 

 analogy between the two processes i in other words, a contraction is a 

 partial death of the muscle/ If this view is correct, then the oxygen 

 is required mainly for heat production through oxidation processes. 



THERMIC PHENOMENA. 



The potential energy liberated during a contraction is transformed 

 into kinetic energy viz., heat and mechanic motion. Though heat 

 production is taking place even during the passive condition, prob- 

 ably through oxidation processes, it is largely increased by muscle 

 activity. The skeletal muscle of the frog, the gastrocnemius, shows 

 after tetanization an increase in temperature from 0.14 C. to 0.18 

 C., and after a single contraction from 0.001 C. to 0.005 C. The 

 amount of heat thus produced will vary with a variety of conditions, 

 as strength of stimulus, tension, work done, etc. 



Stimulus. It has been experimentally determined that an in- 

 crease in the strength of the stimulus from a minimal to a maximal 

 value increases the amount of heat liberated. This is the direct result 

 of increased chemic change naturally following increased stimulation. 



Tension. The greater the tension of a muscle, the greater, other 

 conditions being the same, is the amount of heat liberated. If the 

 muscle is securely fastened at both extremities so that shortening is 

 practically impossible during the stimulation, the maximum of heat 

 production is reached. In the tetanic state the great increase in tem- 

 perature is due to the tension of antagonistic and strongly contracted 

 muscles. In both instances, mechanic motion being prevented, the 

 liberated energy is transformed into heat. 



