20 I'HYsl.iUHiY (IF MUSCLES ANN NERVES. 



angle lift \\een <]ic two parts. To Jin-lit i.iii all tli' 

 various form- of BOcketfl and the movements which they 

 all..\\- \\ould lend us too far; it is sufficient to have 



,-hoWU that the action of the lllliseles is affected by the 

 liones between wllicll they ai'e extended. Ill order, \\n\\- 



ever, to examine the contractile power of muscles, the 

 latter maybe detached from the bones and examined 

 bv themselves. 



/ 



The muscles of warm-blooded animals are but ill- 

 adajited for this purpose ; fortunately, however, those of 

 cold-blooded animaU not only possess the same qualities, 

 but retain the power of contraction long after their re- 

 moval from tlie animal, a circumstance which renders 

 them \ery valuable for purposes of study. The frog is 

 most frequently used in such experiments, both on 

 account of it> common occurrence and of the power of 

 its mu-cles. If a frog is beheaded and an cut ire muscle 

 is cut from either its upper or lower thigh, one of the 

 tendons of this muscle may be fixed in a vice, and 

 its other tendon may be connected with a lever, re- 

 present ing- as it were the bone, by the motion of which 

 the contraction of the muscle may be studied. 1 "Weights 

 may also be attached to this lever in such a way that 

 the burden which the muscle i- capable of lifting may 



be Studied. It Will at ollce be )! (Served that t he muscle 



is extended when such weights are attached, and is 

 extruded more in proportion as the weight attached 



is heavier. This n .-nit - from the elastic qualities of 

 muscle ; and before examining the contraction of muscles 



it will be necearv carefully to study their ela>ti -ity. 



1 In unlrr to fasten the nmsc'lr ni'.n- ,. it is irnirnilly 



\\i-ll t lt-;i\c :i -ln;ill piei-e ut' the l).ine ;it eillier eml ;il t;idiel tn I 



tendons, and \<-> last en the muscle by these. 



