THE ANIMAL AS MACHINE 3/5 



The first example is from a physiological experiment. A dog 

 was subjected to a steady loss of blood at the rate of one per cent 

 of its body weight per minute. Recorded are the three variables : 



(a?) rate of blood-flow through the inferior vena cava, 



(y) „ » » » » muscles of a leg, 



(2) „ » ,, » » gut. 



The changes of the variables with time are shown in Figure 3/5/1. 

 It will be seen that the changes of the variables show a charac- 

 teristic pattern, for the blood-flow through leg and gut falls more 

 than that through the inferior vena cava, and this difference is 

 characteristic of the body's reaction to haemorrhage. The use 



Figure 3/5/1 : Effect of haemor- 

 rhage on the rate of blood-flow 

 through : x, the inferior vena cava ; 

 y, the muscles of a leg ; and z, the 

 gut. (From Rein.) 



Figure 3/5/2 : Phase-space and 

 line of behaviour of the data 

 shown in Figure 3/5/1. 



of more than one variable has enabled the pattern of the reaction 



to be displayed. 



The changes specify a line of behaviour, shown in Figure 3/5/2. 



Had the line of behaviour pointed in a different direction, the 



change would have corresponded to a change in the pattern of 



the body's reaction to haemorrhage. 



The second example uses certain angles measured from a 



cinematographic record of the activities of a man. His body 



moved forward but was vertical throughout. The four variables 



are : 



(w) angle between the right thigh and the vertical 

 [pc) •>■> >» >> leit ,, ,, ,, ,, 



{y) 99 „ » right „ „ „ right tibia 



\~) 5) 5? ?> leit ,, ,, ,, leit ,, 



In w and x the angle is counted positively when the knee comes 



33 



