68 THE ACTIVE FORCES OF LIVING ORGANISMS 



eliminated. In old persons this is a matter of some 

 importance, since they remain under the influence of 

 this excess of carbonic acid for a longer time and to 

 a greater extent than is the case with younger people. 

 In many instances, and especially when there is a 

 tendency to excessive vaso-motor action, a general 

 contraction of the bloodvessels takes place, and is 

 accompanied by pallor of the face. For a space also, 

 owing to the effect of this excess of carbonic acid on 

 the nervous system, metabolism receives a check. 

 This, however, is more than compensated for ere long, 

 for as this effect passes off, the vibrations of the nerve- 

 cells, changing with the altered conditions, swing round, 

 so to speak, to the side of increased oxidation and 

 expansion. The degree of vaso-contraction and of 

 vaso-expansion which occurs in any given instance 

 will depend not only on the extent to which massage 

 may have been carried, but also on the peculiarities 

 of the individual with respect to vaso-motor action in 

 general, and in almost any case they are likely to be 

 somewhat excessive. It is natural — nay, one may say 

 it is inevitable — that the increase of carbonic acid in 

 the blood, dae to the squeezing of the tissues, should 

 affect the vaso-motor centre, for the relations of the 

 vaso-motor nerves to the blood may be supposed to 

 be of a closer nature than those of the other nerves. 

 Massage differs essentially from ordinary exercise in 

 the fact that the carbonic acid is heaped up without 

 any corresponding effort being made to get rid of 

 it, as, for instance, by the increase in the heart's 



