78 LABORATORY MANUAL OF GENERAL PHYSIOLOGY 

 Rate at T2 



In 



■2 = ^/^l _ 1^ 



Rate at Ti 

 Frequency may be expressed as 



Fr^ r u X 100 



Time for ten beats 



Plot log frequency against ^ . , — Cf. Crozier, J. Gen. Physiol., 7: 



571, 1924-25. A critical temperature occurs at 15°C. 



The traditional view is that these movements are controlled by H ion 

 acting on the respiratory centre. ' 'H ions' ' are revealed by a temperature 

 characteristic of 20,000 calories but your value is much lower (5,000 — 

 8,000). Text p. 42. 



3. Opercular Movements of Goldfish. — Place a goldfish in a beaker 

 which fits in a wooden support on top of the thermostat jar. Determine 

 the relation between temperature and opercular moments (5-28°C.). 

 Calculate the temperature characteristic cf. Crozier, J. Gen. Physiol., 9: 

 552. The Arrheniuse quation is discussed in Taylor, "Elementary Physi- 

 cal Chemistry," 1927, p. 167. Reciprocal temperatures may be obtained 

 from Fig. 8, p. 50, Buchanan and Fulmer, "Physiology of Bacteria," 

 vol. 2, 1930. The /i value may be obtained without calculation from the 

 nomogram of Richards, Jour. Phys. Chem., 30: 1219; Buchanan and 

 Fulmer, vol. 2, p. 49. Text pp. 385-395. 



XIII. RHYTHMICITY OF THE HEART 



1. Automatic Rhythmicity of the Heart. — Expose the heart of a frog. 

 Keep moist with Ringer. Determine rate and sequence of beats. Cut 

 widely around the sinus venosus and the veins entering it, sever the two 

 aortae, and thus separate the heart from the body. Place the excised 

 heart in a watch glass. Do the contractions continue? If so, note the 

 rate immediately after the excision and again a few moments later. 



Cut between sinus and right auricle at the sinoauricular junction. 

 Does the sinus continue to beat? (It will be necessary to wait until the 

 immediate effects of cutting have disappeared.) Does the rest of the heart 

 now beat? And if so, at what rate? 



Cut between auricles and ventricle, just above auriculoventricular 

 groove. Do contractions occur in the isolated parts? 



Cut through the ventricle, just below the auriculoventricular groove. 

 Does the apex beat? Stimulate it, by tapping it, and by a crystal of NaCl. 

 According to Heinbecker and Bishop, Am. J. Physiol., 114: 212, 1935, 

 the ventricle of the turtle is free of ganglia and therefore cannot beat. 



2. The Stannius Ligature (Preparation for Ex. 3). — The automatic 

 contraction of the ventricle can be inhibited by means of a "Stannius 



