502 



APPENDIX 



From some source (perhaps from a progressive anabolism in the 

 protoplasm, possibly from the nervous system), the normally beating 

 heart receives a constant stimulation. The galvanic current may 

 serve as a substitute for the normal stimulus whatever it is, and occa- 

 sion similar reaction. Other muscle does the same, for example the 

 ureter, the dartos, and in some cases the intestinal muscle. 



Expt. 65. No Cardiac Tetanus f (Apparatus: Needle, thread, 

 inductorium, key, kymograph, etc., heart-lever.) Apply the first 

 Stannius ligature (around under the sinus venosus) as described in 

 Expt. 61. Place the quiet heart in the heart-lever, connect the latter 

 with the inductorium arranged for tetanizing currents (with the armature 

 vibrating), and arrange the lever to write on a slowly rotating drum. 

 Stimulate the heart with three strengths of this alternating current, 

 weak, medium, and maximal, each for a series of ten or more beats. 

 Nothing like the tetanus-curve of cross-striated or of smooth muscle is 

 produced. 



FIG. 279 



Normal frog-cardiogram by the suspension-method. The auricular beat occurs first. To be 

 read from left to right. Original size. The time-line is in seconds. 



If the frog's heart, however, be warmed to 35 and such a current be 

 sent through the heart, something approaching tetanus is produced in 

 the organ. This is thought to be abnormal; it is perhaps a degree of the 

 torpidity due to heat rigor, or to the coagulative death of the cardiac 

 protoplasm. The matter, however, needs further study. 



Expt. 66. Temperature Affects Contraction. (Apparatus: Heart- 

 lever, kymograph, chronograph, etc., Ringer's fluid at 3 and at about 

 40, pipets.) 



(A) Put the normal heart in connection with the heart-lever and make 

 a series of cardiograms on a drum rotating slowly; by a watch make on 

 the curve a short mark exactly every ten seconds, or use the time-marker. 

 This record shows the rate of the heart at a room temperature, about 

 18. Determine exactly this rate per minute. 



(B) Start a cardiogram on a lower drum-level. With a large pipet 

 drop by drop add the modified cold Ringer's solution to the heart. 

 Observe that the heart at once slows. Measure off the cardiogram 

 into ten-second periods as before, and calcutate the cold pulse-rate per 

 minute, and the percentage of retardation. 



