116 W. A. Osbovne: 



yawning may find a partial explanation here), but in disease, as 

 Haldane pointed out later, the oscillations may become large and 

 obvious, producing the Cheyne-Stokes breathing, which is so strik- 

 ing a clinical sign. Here we find conformity to the rule that an 

 inadequate or deranged regulator will be made manifest by an 

 increase in the amplitude of the oscillation. 



II. Body Temperature. — A great advance in evolution was the 

 rise of the homoiothermal bird and niannnal. In poikilothermal 

 creatures metabolism is a function of the air temperature, and comes 

 almost to a standstill in the winter of certain climates. A poikilo- 

 thermal man could not make definite plans or enter into definite 

 contracts for the performance of work except in tlie tropics as the 

 ability to labour would rise and fall as the air was warm or cold. 

 Now the temperature of a bird or mammal is not absolutely con- 

 stant. Vigorous muscular movement, as is well known, may, even 

 in an English winter, drive the temperature up to fever pitch; 

 normality is resumed quickly if the air is cold, slowly if the air is 

 hot and humid. The temperature chart of a healthy human being 



■ is by no m.eans a straight line. Even when metabolism is kept fairly 

 constant, as when the subject of the experiment remains fasting in 

 bed, a marked diurnal oscillation is apparent, which may have an 

 amplitude of as much as O.SoC.^ Whetlier this oscillation is that 

 due to self-regulation or is more properly a periodicity effect, is, 

 however, not very clear. Much more likely to be the oscillations 

 in question are those small irregular waves displayed when thermo- 

 electric records are graphically taken. Again, we find that a de- 

 ranged m.echanism will produce an exaggerated amplitude of 

 rhythm. In convalescence from an illness, particularly an illness 

 accompanied by fever, exertion that would not in health affect the 

 adjustment, is sufficient to provoke a decided elevation of tempera- 

 ture, and lead to copious sweating, which, in its turn, can very 

 easily produce subnormality when the exercise ceases. 



III. The Muscular System. — It will be evident that if the posi- 

 tion assumed by a limb is one extreme of movement, if, for instance, 

 extension be carried as far as the ligaments on the flexor side will 

 allow, the fixation here is mechanical, and no oscillation need he 

 expected. In reflex postural contraction it is also probable that 

 an arhythmical fixation is present for the tension may here be 

 purely elastic, the contractile substance being fixed by a hook 

 mechanism (Grutzner)2, or through gel formation (Sherrington) 3. 



1 See article Die Wiiniiei'.kononiie des Kiirpers, by I!. Ti^'evstedt in Nagel's HaiKlbuch. 



2 See Bayliss, Principles of General Physiolosf.v, 1915, p. 534. 



3 Postural Activity of Muscle and Nerve. Brain, 1915, vol. 37, p. 191. 



