72 



ANIMAL MECHANICS. 



by a muscle, during a single contraction. When human 

 muscles are moderately used, their maximum force per square 

 inch of cross section is found to be : 



102.55 av - lbs- per sq. in., or 7.225 kilos, per sq. centimeter ; 



but the muscles of all animals are capable of being stimulated 

 for a time to perform an amount of work much greater than 

 that done under ordinary circumstances. 



The following results, obtained by Matteucci and Helm- 

 holz, from experiments made upon the muscles of the calf of 

 the frog, exhibit this principle very clearly. It will be ob- 

 served that the total work done in a single contraction of the 

 muscle increases with the weight it is compelled to lift. 



TABLE IX. — Work done in a Single Contraction by the Gastro- 

 cnemic Muscles of the Leg of a Frog. 





Weight lifted. 



Height. 



Work done. 



Observer. 



1°. 



2°. 



3°- 

 4°- 

 5°- 



10.32 grms. 



40.3 2 » 



7o.3 2 

 100.32 

 180.32 ,, 



1.412 mm. 

 1.270 „ 



1. 130 „ 

 0.840 „ 

 0.765 „ 



14-57 

 51.21 

 79.46 

 84.27 

 137-94 



Matteucci. 

 Helmholz. 



The most complete series of experiments on the gastro- 

 cnemius of the frog are those made by Mr. Baxter, who found, 

 as the result of the examination of 60 frogs, of whom 26 were 

 females — 



Total weight of muscles, . 262 grs. 

 Total weight lifted, . . . 159360 grs. 



From these experiments we find the average forge of the 

 frog's gastrocnemius— 

 159360 



— = 2656 grs, = 172-11 grms. 



