ANIMAL AND VEGETABLE 257 



throughout, but owing to local pyrexia at b the level is 

 altered and the diagonal may become 



.-.air 



Fig. 143 B . 



giving the effect of increased pressure and consequent 

 greater flow. 



Not only is this so, but as a local rise of temperature 

 lowers the level of issue, it, at the same time, enlarges the 

 diameter of the pipe, in the area affected, by increasing the 

 conductivity of the moist conductor, the nerve-substance ; 

 so that we have not only a lower level, but what may be 

 likened to an artificial head of water created in the path a, b. 



Similarly alterations of resistance in the form of added 

 resistance due to disease may be thought out. Between 

 acute local pyrexia, such as lobar pneumonia with a body 

 temperature of 106 F. involving, possibly, a local 

 temperature of 116 F. and cancer, there would be the 

 widest margin, because the cancer cells are devoid of 

 conductivity. In the latter case our diagram might 

 become 



.cur 



Fig. 143c. 



and there would not be any flow at all from a to b. 



There are many gradations between the two extremes, 

 but after due allowance has been made for skin conditions, 



