486 Dynamic Theory. 



with teeth. They swallow their food without mastication, and will 

 swallow artificial bait readily enough if natural in appearance. In rep- 

 tiles and amphibians too, the sense of taste seems to be confined to such 

 semblance of it as may reside in the nostrils. Those of them that pos- 

 sess tongues that are extensible, like the snakes, toads, frogs and 

 chameleons, use them as organs of touch, or weapons for striking and 

 taking prey. The birds, inheriting from the reptiles, have probably 

 not retrograded, but they show little or no advance in the sense of taste. 

 The sense of smell in them is well developed, as an aerial sense. But 

 their tongues are generally cartilaginous, and they often swallow their 

 food without mastication. The tongue of the woodpecker is barbed at 

 the point, and is simply a weapon for taking prey. Parrots have a 

 fleshy tongue and are supposed to possess a better sense of taste than 

 any others. ( Cuvier.) This sense is greatly a creature of habit, and 

 may become accustomed to the nicest discrimination of flavors, as in 

 the case of wine tasters and tea drinkers, &c. 



CHAPTER LI. 



PHYSIOLOGY OF THE MUSCLES. 



Contraction in a longitudinal direction results from the magnetization 

 of certain conductors of yielding constitution. ' ' Let discharges from 

 a Leyden jar or battery be passed through a platinum wire too thick to 

 be fused by the discharges and free from constraint, it will be found 

 that the wire is shortened. It has undergone a molecular change, and ap- 

 parently been acted on by a force transverse to its length. If the dis- 

 charges be continued, it gradually gathers up in small irregular bends or 

 convolutions. So with voltaic electricity. Place a platinum wire in a 

 trough of porcelain so that when fused it shall retain its position as a 

 wire, and then ignite it by a voltaic battery. As it reaches the point of 

 fusion it will snap asunder, showing a contraction in length, and conse- 

 quently a distension or increase in its transverse dimensions. Perform 

 the same experiment with a lead wire, which can be more readily kept 

 in a state of fusion, and follow it as it contracts by the terminal wires 

 of the battery ; it will be seen to gather up in nodules which press on 

 each other like a string of beads of a soft material, which have been 

 longitudinally compressed. * 



Prof. Owen uses the following language : 2 Amber or steel, when 

 magnetized, seem to exercise selection ; they do not attract all substances 

 alike. To the suitable ones, at a due distance, they tend to move, but 

 through density of constitution cannot outstretch thereto ; so they draw 



1 Correlation of Physical Forces, 95. 2 Anat. of Vertebrates, Vol. 3, 818. 



