Echocardiography was performed on 119 dogs weighing 1.8 to 28 Kg to examine the cardiac function. An Aloka echocardiograph (Nihon Musen Igakukenkyujo, Fukuda Denshi Co., Ltd. model SSD-110, M mode type) was used.
1) Mitral, aortic, tricuspid and pulmonary valve echograms and ventricular wall echograms were recorded even from small dogs by using the instrument improved at the magnification rate, sweep speed, cycle of beam and seize of transducer.
2) When the transducer was placed on the third, fouth or fifth left intercostal sternal border, a mitral valve echogram was most readily recorded, showing an M-type wave. An aortic valve echogram was presented as a linear echo between two parallel echos at the systole, and as a rectangular echo at the diastole. A tricuspid or pulmonary valve echogram was hardly recorded in succession. 3) When the transducer was placed on the right sternal border, a tricuspid or pulmonary valve echogram was well recorded in dogs with hypertrophy of the right ventricle or projection of the pulmonary artery.
4) An echocardiographic diagnosis could be made in the case of heart diseases, such as mitral insufficiency and the vena cava syndrome.
From these results, it was presumed that an echocardiogram might be available for the examination of cardiac function in the same manner as an electrocardiogram and an electrophonogram.

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Electrocardiographical characteristics of the beagle, as an experimental dog, were investigated in 102 individuals of both sexes, in comparison with 137 mongrel dogs, by using A-B bipolar lead. Moreover, in 20 beagles and 20 mongrel dogs selected from them, electrocardiograms were also recorded by using limb leads, precordial leads and supplementary precordial leads. The results obtained are summarized as follows.
1) No differences were observed in the conduction time between beagles and mongrel dogs. The amplitude of each deflection (P, R, S and T waves), however, was higher in the beagles than in the mongrel dogs. The ratio of amplitude of S wave to T wave was higher in the beagles.
2) C₆ lead ECG in the beagles appeared in the Qr type of the QRS complex, and that in the mongrel dogs in the RS type with a higher amplitude. M₅ lead ECG in the beagles presented the Qr type of the QRS complex, although that in the mongrel dogs showed the qR type. In C₁lead ECG, each dog showed the Qr type of the QRS complex with the same amplitude.
3) From the above-mentioned results, it was presumed that the heart might be larger in size in the beagle than in the mongrel dog, as compared with the volume of the thoracic cavity. In the beagle, the right ventricular wall might widely cover the cranial part of the right thracic wall, accompanied with a slight anticlockwise rotation around the longitudinal heart axis.
4) No arrhythmias were observed in the beagles at any lead of ECG. Much fewer abnormalities in ECG pattern were seen in the beagles than in the mongrel dogs.

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Ventricular paroxysmal tachycardia was recorded by radiotelemetric ECG while walking for about 50 meters.
This arrhythmia was cured with ATP. Dogs were administered orally with 20 mg of ATP twice a day, or 40 mg per day. It was supposed that the results might be due to the coronary dilating effect of adenosine.

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