374 THE EFFECTS OF FOOD. [BOOK i. 



which at the time are or ought to be at rest and therefore 

 requiring comparatively little blood. These organs certainly at 

 all events ought not during exercise to be engaged in the task of 

 digesting and absorbing food, and the old saying, " after dinner sit 

 awhile," may serve as an illustration of the working of the vascular 

 mechanism with which we are dealing. The duty which some of 

 the digestive organs have during exercise to carry out in the way 

 of excretion of metabolic waste products is as we have already 

 said probably taken on by the flushed and perspiring skin. It is 

 true that at the beginning of a period of exercise, before the skin 

 so to speak has settled down to its work, an increased flow of 

 urine, dependent on or accompanied by an increased flow of blood 

 through the kidney, may make its appearance ; but in this case, 

 as we shall see later on in dealing with the kidney, the flow of 

 blood through the kidney may be increased in spite of constriction 

 of the rest of the splanchnic area, and, besides, such an initial 

 increase of urine speedily gives way to a decrease. 



The 'distress' which follows upon undue exertion is also 

 exceedingly complex. It tells upon the breathing, upon the 

 heart, upon the whole nervous system, and even on the muscles 

 themselves. We can only refer briefly to the heart. 



We have seen ( 158) that the action of the augmentor 

 mechanism in contrast to that of the inhibitory mechanism leads 

 to exhaustion. Hence during exercise it is desirable that the 

 augmentor mechanism should be brought into play as little as 

 possible ; indeed we may perhaps suppose that it is not brought 

 into action during exercise to any great extent until the waste 

 metabolic products have accumulated in the blood beyond a certain 

 extent; the increased work of the heart is probably up to this 

 point chiefly due to the increased venous inflow. And possibly 

 one effect of training for exercise is to bring about such a con- 

 dition of the body as will get rid of these products as speedily as 

 possible and so limit the call upon the augmentor mechanism. 



In distress on the other hand we may probably recognise in 

 the heart the exhaustion consequent upon augmentor action ; 

 but matters are made still worse by the injurious direct action on 

 the cardiac tissue of the waste metabolic products. The two so 

 weaken the heart that the ventricles are no longer able to dis- 

 charge into the arteries the proper quantity of blood and, the 

 venous inflow still continuing, become abnormally distended. If 

 the cardiac tissue be already enfeebled by disease this condition 

 of things may lead to a cessation of the beat and so to death ; but 

 in a healthy organism such an end is probably in most cases, 

 forestalled by the altered blood acting even more injuriously on 

 other organs of the body. 



194. The effect of food on the vascular mechanism affords a 

 marked contrast to the effect of bodily labour. The most prominent 

 result is a widening of the whole abdominal vascular area, accom- 



