94 LABORATORY MANUAL OF GENERAL PHYSIOLOGY 



of quiescence). Determine the rate. Repeat with excised leg (cf. 

 Crozier and Stier, J. Gen. Physiol., 10: 479, 1927). 



CRUSTACEAN HEART 



In the lobster the heart consists of a sac of striated muscle with 4 ostia 

 through which the blood enters. 



Cut a window on the top of the carapace and attach heart lever with 

 thread and a fine hook. Tie thread near fulcrum for greater leverage. 

 As these hearts are perishable do not bother with signal magnet or timing 

 device. Perfuse with Marine Crustacean Ringer (NaCl 0.5M, CaCl2 

 0.04M, KCl .OlM). Record on lightly smoked drum. 



4. Ca-K Paradox in Crustacean Heart. — Drop 0.5M CaCl2 on the beat- 

 ing heart and note arrest in diastole (unlike vertebrate heart). Cf. 

 Hogben, "Comp. Physiol.," p. 17, 1926. Irrigate with Crustacean Ringer 

 until recovery and apply 0.5M KCl which favors systole. Irrigate with 

 Ringer for recovery. Text p. 440. 



5. Tetanus in Crustacean Heart. — Place fine wires from an inductorium 

 at each end of the heart and obtain a record under weak tetanizing current. 

 The brothers Weber (1846) noted that crustacean heart shows no refractory 

 period and summation and tetanus can be easily obtained (cf. Clark, 

 "Compar. Physiol, of Heart," p. 9). Compare record with that of 

 tetanized frog skeletal muscle. Text p. 432. 



MOLLUSCAN HEART 



The circulation in Molluscs is much more highly developed than in 

 Arthropods. In the clam (Venus) the heart consists of a large ventricle 

 (through which the intestine runs) and 2 thin-walled auricles (all smooth 

 muscle). For oyster heart cf. Walzl, Physiol. Zool., 10: 125, 1937. 



Remove one valve of the shell and open the pericardial cavity (near the 

 hinge). Attach the heart lever thread to ventricle with a fine hook. 

 Place the clam in a finger bowl containing Marine Molluscan Ringer 

 (NaC10.4M,CaCl2.005M,MgCl2.08M). Record the beat. Immediately 

 after exposure the heart may remain temporarily at rest. Open several 

 clams until a satisfactory heart is obtained. If clams are kept on ice 

 they should be exposed to room temperature a few hours before experiment. 



6. K Systole in Clam Heart. — Remove the Ringer from the bowl and 

 obtain a record of the effect of dropping M/2 KCl on the heart. Now add 

 M/2 CaCl2 and note the change. Return the clam to Ringer for a recovery 

 record (for ionic effect, cf. Clark, p. 135). For effects in oyster heart cf. 

 Jullien and Morin, Jour. Physiol, et Path. Gen., 29: 446, 1931. Text p. 440. 



7. Effect of Adrenalin on Clam Heart. — Note the augmentor action of 

 adrenalin. In vertebrates the inhibitory actions of adrenalin on various 

 tissues are as common as augmentor effects but in invertebrates only 

 augmentor action has been described (Clark, p. 62). 



