468 GENERAL PHYSIOLOGY 



picture of events in acute infectious diseases. The conjecture is 

 strongly suggested that all these symptoms that appear as a result 

 of muscular fatigue appear also as the characteristic complex of 

 symptoms of infectious diseases. Concerning the latter, it is known 

 from the later bacteriological investigations that they are the 

 result of poisoning by certain poisonous metabolic products, the 

 so-called toxines, 1 which are excreted by invading bacteria. But, 

 like bacteria, a great variety of other forms of living substance 

 excrete poisonous substances in their metabolism, and hence the 

 assumption is not unjustified that the muscles also produce such 

 toxines, which in the quantity usually present produce no effects, but 

 which, as soon as they accumulate in the body in greater quantity 

 as the result of excessive muscular activity, give rise to phenomena 

 of genuine poisoning. Various experiments have proved directly 

 that this conjecture is correct. 



The first important experiments were those of Eanke ('65), who 

 found that he could make a fatigued muscle again capable of 

 performing work by washing it out with a dilute solution of 

 common salt which, as is well known, is completely indifferent to 

 living tissue. Hence there must have arisen and accumulated in 

 the muscle as the result of activity certain fatigue-substances, 

 which act to paralyse the muscle-substance itself, but after the 

 removal of which the muscle regains its capacity for work. Ranke 

 was able actually to confirm this by the following experiment. He 

 made a watery extract of muscles that had been strongly fatigued, 

 and injected it through the blood-vessels into a fresh muscle. 

 The result was that the muscle immediately lost its working 

 capacity and behaved exactly like a fatigued muscle. It is 

 proved by this experiment that phenomena of fatigue are caused 

 by the accumulation of certain metabolic products in the muscle, 

 and can be set aside by the washing-out of the latter. More 

 recently Mosso ('91) performed upon a dog an experiment an- 

 alogous to Ranke's. When he injected into a narcotized dog blood 

 from a normal dog, the former continued completely normal. But 

 if, instead of this, he used for injection blood from a fatigued dog, 

 whose muscles had been kept in violent contraction by tetanization 

 with the electric current for only two minutes, characteristic 

 phenomena of fatigue immediately appeared : the respiration 

 became accelerated and even dyspnceic, and the heart began to 

 beat strongly. Hence the fatigue-substances that are produced in 

 the muscle do not remain there, but are taken up by the blood 

 and thus go to the organs of the whole body. Hence it comes 

 about that after an exhaustive march not only do the muscles of 

 the legs, but also those of the arms, show phenomena of fatigue. 

 The poisonous substances going with the blood to the brain-centres 

 that control respiration and the movement of the heart, there first 



1 Of. p. 175. 



