6 LABORATORY MANUAL OF GENERAL PHYSIOLOGY 



spheres. Avoid injury to other parts. Place the worm for a few minutes 

 in water to recover from the anesthetic. 



Repeat Exps. 4, 5, and 6. Has sensitivity diminished? Will the worm 

 spontaneously burrow in earth? Place the anterior end under earth. 



9. Homostrophic Reflex (By which the anterior and posterior ends 

 are kept parallel). — Displace to one side the tail end of an earthworm 

 which is creeping in a straight line. Observe the orientation of the head 

 end. Repeat with a worm lacking the first 20 segments. 



10. Inhibition of Homostrophic Reflex by Stereotropism. — Allow a 

 worm to crawl in contact with a glass plate. As it rounds the comer 

 remove the plate and observe the homostrophic reflex released with con- 

 tact removed. Meal worms (Tenebrio) may be used if available. Cf. 

 Crozier, J. Gen. Physiol., 5: 597, 1923. 



11. Evidence for Reciprocal Inhibition. — Inject a worm with strych- 

 nine sulphate 1/10,000 and compare its locomotory movements with those 

 of a normal worm. Avoid injecting alimentary canal (cf. Knowlton 

 and Moore, Am. J. Physiol., 44: 490, 1917). 



12. Nerve Plexus. — Cut out a section, about 20 segments, from the 

 middle of a worm. Carefully remove the alimentary tract and ventral 

 nerve cord. Any spontaneous movement? Stimulate with a needle and 

 with a weak electrical shock. Does conduction travel in all directions? 



13. Muscle Tension. — Anesthetize cutaneous receptors of a worm by 

 immersion in M/8 MgClo until gentle stroking with a brush elicits no 

 response. Make a muscle preparation from the mid-body region and 

 connect to a light lever writing on a kymograph as shown in demonstra- 

 tion. Does the muscle make spontaneous contractions? Now weight 

 the muscle with 1 or 2 grams and record contractions (cf. Moore, J. 

 Gen. Physiol., 5: 327, 1922). If this experiment does not work use the 

 preparation for a smooth muscle record on the kymograph. Stimulate 

 electrically with fine wires. 



14. Stereotropism in Isopods. — Allow a sow bug to crawl with one 

 surface in contact with a glass plate and observe the direction of turning 

 when the plate is passed. Place the isopod so that it crawls between the 

 edges of two plates and observe the subsequent direction. Repeat but 

 remove one plate just before the animal reaches the end of the passage 

 (cf. Crozier, J. Gen. Physiol., 6: 531, 1924). 



15. Chemical Trap Action of Jennings. — Place a drop of M/80 HCl 

 on a glass plate containing a thick suspension of Paramecium. Observe 

 the edges of the drop. Place a drop of 0.02% acetic acid containing Para- 

 mecium on a slide of culture medium. Do the animals stay in the acid? 

 To prove that these reactions are not chemotropic, proceed as follows. 

 Fill four capillary tubes with (1) culture medium, (2) distilled water, 

 (3) M/180 HCl, (4) 0.02% acetic acid. Introduce the ends into a large 



