218 MOUNTAIN SICKNESS 



the consumption, but only for the particular combination of 

 muscles used in walking hence the advantage of change of 

 work. The volume of air breathed increases from 8 1. per min. 

 resting, to 16 1. walking on the flat, and to 26 1. climbing. In 

 steep climbing the volume may even be fivefold that resting. 

 Fatigue from over- walking renders the respiration shallow and the 

 pulse frequent. Over-strain causes a marked rise of body 

 temperature, increased N 2 output, dilatation of the heart, sinking 

 of the vascular tone. The kidneys secrete a dilute urine, and 

 albumin may appear owing to congestion of the blood-vessels. 

 Poisonous products of metabolism are produced in fatigued 

 muscles, and extracts of these appear to be extremely toxic to 

 normal animals. Immunity can be established by giving small 

 doses of these extracts, and it has been suggested that training 

 partly consists in the immunisation of the body against fatigue 

 products. 



Zuntz and Schumberg observed soldiers marching, and found 

 they could carry a load of 22 kg., and march 15-20 km. 

 without noticeable rise of body temperature. After a birthday 

 drinking bout, however, the body temperature rose to 39' 3, and 

 40-5 during the march. A load of 22 kg. has a significant effect 

 on the untrained, while the trained soldier is hard put to it 

 under a load of 31-5 kg. About 20 kg. is the limit of load which 

 should be put upon the soldier, and this should be distributed so 

 as not to disturb the equilibrium of the body. The vital capacity 

 is lessened by the load hampering the movements of respiration, 

 and the systole of the heart is prolonged even to 30 per cent, by 

 a load of 18 kg. 



When the breathing becomes as frequent as 35 per min. or 

 more and shallow from fatigue, the phenomena of cardiac dilata- 

 tion and venous congestion, such as increased cardiac dulness and 

 enlargement of the liver, became marked. The frequency of 

 respiration should not increase more than 75 per cent, during the 

 march, and should not be more than 30 per cent, above normal 

 after a 15 min. rest. This is an easy test for a man to apply 

 to himself. 



Over- work leads to destruction of muscle substance and long 

 lasting diminution of functional power. Fatigue leads to a less 

 economical use of the muscles, and increases the Calories expended 

 in work by 5-9 per cent. 



