90 ORGANIC FUNCTIONING 



34. ON CO-ORDINATION AND REGULATIONS OF 



FUNCTIONING 



It is convenient in exposition, and quite necessary in investiga- 

 tion to deal analytically with organs and modes of functioning 

 and behaviour. Nevertheless, it is true to say that the animal 

 body behaves and functions as one thing. Thus if an animal 

 makes some violent exertion everything in its body participates 

 in that activity. The muscles apply forces to the moving limbs 

 and other parts ; the rate of beat of the heart increases ; the 

 respiratory organs function more vigorously ; glycogen is dis- 

 charged from the liver (or other reserves are mobilized) and so on. 



24a. Integration of Functioning. The whole nervous 

 system is an integrative organ, connecting together all parts and 

 co-ordinating all activities. The blood-stream, which is a con- 

 tinuous fluid in all organs, receives excretory products from all and 

 gives materials to all. The common framework of connective 

 tissue that is everywhere in the body is not only a common 

 mechanical structure but has, possibly, some chemical function 

 and so on. Thus everything that happens anywhere aifects, in 

 some degree, everything else. Every bodily activity, though it 

 is mainly expressed as some behaviour-pattern, involves many 

 other neuro-muscular mechanisms than the characteristic one and 

 the organic functioning which energizes the muscular activities 

 involves most, or all, of the metabolic organs. 



It necessarily involves oxidations of carbohydrates so that the 

 muscle stores of those substances must be made good from the 

 circulating blood. On the other hand, the latter becomes loaded 

 with CO 2 which must be eliminated. In bodily activities the 

 composition of the blood must tend continually to change, yet 

 its constancy of composition and its reaction vary only within very 

 narrow limits. This constancy is maintained by the functioning 

 of the metabolic organs. 



34^. Regulatory Mechanisms. Mainly these are nervous 

 and muscular. They are automatic and the automatism may be 

 regarded as the expression of a need — ^that of organic normality. 

 Heat-regulation, for example, in the mammal depends largely 

 on a nerve-muscle mechanism : the need is for a constant bodily 

 temperature. Should this rise, the muscles in the walls of the 

 arterioles of the skin dilate ; there is an increased blood flow just 



