THE CONTRACTILE TISSUES. 167 
is formed. This, in the higher vertebrates, ends in tough, 
inelastic extremities suitable for attachment to the levers it 
may be required to move (bones). 
Fra. 158. Fie. 159. 
Fie. 158.—Muscular fibers from the urinary bladder of the human subject. 1 x 200. (Sappey.) 
1,1, 1, nuclei ; 2, 2, 2, borders of some of the fibers ; 3, 3, isolated fibers ; 4, 4, two fibers 
joined together at 5. 
Fic. 159,—Muscular fibers from the aorta of the calf. 1x 200. (Sappey.) 1, 1, fibers joined 
with each other ; 2, 2, 2, isolated fibers. 
Comparative.—The lowest animal forms possess the power of 
movement, which, as we have seen in Ameceba, is a result rather 
of a groping after food; and takes place in a direction it is im- 
possible to predict, though no doubt regulated by laws definite 
enough, if our knowledge were equal to the task of defining 
them, 
Those ciliary movements among the infusorians, connected 
with locomotion and the capture of food, are examples of a pro- 
toplasmic rhythm of wonderful 
beauty and simplicity. 
Muscular tissue proper first 
appears in the Celenterata, but 
not as a wholly independent 
tissue in all cases. In many 
celenterates cells exist, the low- _ - ; 
er part of which alone forms a ™% 1—Myoblaste of a jelly-fish, the Me- 
delicate muscular fiber, while 
the superficial portion (myoblast), composing the body of the 
cell, may be ciliated and is not contractile in any special 
