134 



EXTENSIBILITY AND WORK OF MUSCLE. TCH. xi. 



greatest when the muscle is in a contracted condition, and 

 smallest when it is dead (in rigor). In fatigue the after extension 

 is very marked, and the return after unloading very imperfect. 



We may now give the results of an actual experiment ; a 

 muscle Avas loaded with successive weights of 50, 100, 150, etc., 

 grammes, and its length carefully measured in centimetres. 



Load .... 50 100 

 Total extension . . 3-26 

 Increment of extension 2*8 



150 



200 250 300 

 9-5 10 10-3 

 i'5 0-5 0-3 



In rigor 



In tetanus 



Normal 



Figure 156 shows that the contracted muscle is more exten- 

 sible than the uncontracted muscle. This may be still further 



illustrated by an example given 

 on the opposite page in the form 

 of a diagram. 



The thick lines represent the 

 contracted muscle, the thin ones 

 the uncontracted. It is repre- 

 sented as being stretched by dif- 

 ferent weights indicated along 

 the top line ; and the lengths 

 under the influence of these 

 weights are separated by equal 

 distances. Thus A C represents 

 the length of the uncontracted 

 muscle, A B of the contracted 

 muscle when unloaded. A' C' 

 and A' B' the same under the in- 

 fluence of a weight of 50 grammes, 

 and so on. 



The curve connecting the ends 

 of the lengths of the contracted 

 muscle falls faster than that 

 obtained from the uncontracted 

 one, until at the point P under 

 the influence of a weight of 250 

 grammes, the two curves meet ; 

 that is to say, 250 grammes is 

 the weight which the muscle is 

 just unable to lift. Suppose a 

 muscle has to lift the weight of 

 200 grammes, it begins with a length A" C", but when it con- 

 tracts it has a length A" B", that is, it has contracted a distance 

 of B" C", which is very small ; when it has to lift a less weight 



Fatigued 



Fig. 156. Extensibility of muscle in 

 different states ; tested by 50 grammes 

 applied for short periods. "Tracings to 

 be read from left to right. 



Waller.) 



(After 



