MATTER AND CELLS 



17 



to that of the amoeba. Fresh blood may be obtained by pricking the 

 finger with a sterilized needle, and by decapitating or pithing a frog. 



3. Movements of Protoplasm 

 in Plants. The phenomena 

 of protoplasmic movements 

 can be observed in a variety 

 of plants. The Stoneworts, 

 Chara and Nitella, and the 

 stamen hairs of the Spider- 

 wort, Tradescantia, furnish 

 some of the best examples. 

 In all these the protoplasm is 

 inclosed in a cell wall, and 

 when observed with the com- 

 pound microscope is seen to 

 exhibit streaming movements 

 and circulation of particles in 



Fig. 5. Compound microscope with sim- 

 ple warming stage (W) attached. 



the contents of the cell. The 



response of protoplasm to 



changes in temperature can 



be very easily shown by placing the slide on a warming stage upon 



the microscope stand as shown in Fig. 5. When the warming stage 

 is heated, the protoplasmic movements a,re seen to 

 increase in rapidity up to a certain point. As it 

 cools, the movements become slower. 



4. Properties of Protoplasm in Muscle. In some 

 animals the various tissues retain their vitality and 

 properties for a considerable time after the death 

 of the individual animal. The common frog fur- 

 nishes us one of the best examples of this. If a 

 frog's gastrocnemius muscle with sciatic nerve at- 

 tachments (Fig. 6) be dissected out (see Figs. 7 

 and 8) shortly after decapitation of the animal, it 

 will retain its properties for a considerable length 

 of time, if kept well moistened with normal salt 

 solution (0.75 per cent solution of common salt). 

 If the nerve be cut with sharp' scissors a contrac- 

 tion of the muscle occurs. Touching the nerve 

 with a red-hot needle produces a similar contraction 



FLg. 6. Nerve- 

 muscle prepara- 

 tion. 



F femur. 



G gastrocnemius 



muscle. 



S sciatic nerve. 

 T tendon (tendo 



Achilles). 



MACY'S PUYS. 2 



