GIL XXV II.] 



TISSUE RESPIRATION 



397 



At the point D the renal vein was compressed, and at the point 

 E the compression ceased. From D to E the inflowing blood caused 

 the kidney to expand and the recording lever to rise. It crosses the 

 two horizontal lines at F and G respectively. During this time 

 (F to G), therefore, half a cubic centimetre of blood entered the 

 kidney, and this time was thirty-three vibrations of the time-marker, 

 that is 1-1 second. Hence the rate of blood-flow would be 



:p: = 27-3 c.c. of blood per minute. 



In order to measure the gaseous exchange of an organ over a 

 long period the organ is supplied with blood which alternately 

 traverses the organ and aerates itself in a closed chamber. The 

 amount of oxygen in the chamber is kept constant by the addition of 

 that gas to the air of the chamber at the same rate at which the 

 circulation acquires it. The amount of oxygen so added is measured. 

 The method has recently been applied with conspicuous success to 

 the gaseous exchange of the heart. 



Relation of Tissue Respiration to Functional Activity. 



In all organs, so far as is known, increased activity is accom- 

 panied by increased oxidation. 



Much interest centres about the question of the order of time 

 in which these events take place. This matter has been investigated 



FIG. 



minutes 



. Tiie black-white line represents rate of salivary secretion in c.c. per minute. S S= 

 line for saliva. Black area = oxygen used by the gland. 0= oxygen base line. 



in the case of skeletal muscle and the submaxillary gland (fig. 309), 

 both of which organs can be thrown into profound activity for a short 

 space of time ; in each case most of the oxidation follows upon the 

 activity, and not the activity upon the oxidation. The important 

 inference is drawn that the contraction or secretion, as the case may 

 be, is not caused by the oxidation in the sense that the machinery of a 

 locomotive is driven by the energy derived from the oxidation of the 

 coal ; rather is the mechanism like that of a spring which is 

 liberated at the moment of doing the work, and has to be rewound 

 subsequently ; the process of rewinding involves oxidation. In the 

 case of muscle, the heat-formation which occurs in the period 



