ROBERT L. HAMLIN AND C. ROGER SMITH 
615 
sidered normal in certain mammals but consid- 
ered to be abnormal in man. 
Differences exist in postures within the tho- 
rax of hearts of quadrupeds compared with 
hearts of primates. Even though cardiac activa- 
tion may be identical in certain quadrupeds and 
primates, body surface potentials of one may be 
grossly different from surface potentials of the 
other. 
REFERENCES 
1. Hamlin, R. L., J. Himes, H. Guttridge, and W. 
KiRKHAM. P wave in the electrocardiogram of the 
horse. Am. J. Vet. Res. 31:1027-1031, 1970. 
2. Hamlin, R. L., D. L. Smetzer, T. Senta, and C. R. 
Smith. Atrial activation paths and P waves in 
horses. Am. J. Physiol. 219:306-313, 1970. 
3. Lannek, N. a clinical and experimental study of 
the electrocardiogram in dogs. Thesis, Stockholm, 
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6. Hamlin, R. L., S. Ridgway, and W. Gilmartin. 
Electrocardiogram of pinnipeds. Am. J. Vet. Res. 
(Accepted for publication in March, 1972). 
7. Hamlin, R. L. and C. R. Smith. Categorization of 
common domestic mammals based upon their ven- 
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8. DuRRER, D. and L. H. Van der Tweel. Excitation 
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Multichannel recording apparatus for physiologic 
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The electrocardiogram, phonocardiogram, and de- 
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cardiogram and vectorcardiogram of normal 
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lateral and sitting positions. Biomedical Laboratory 
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1960. 
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lead, spatial magnitude, and spatial velocity elec- 
trocardiograms, and vectorcardiograms of turkeys. 
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orthogonal lead system in the horse. Am. J. Physiol. 
207:325-333, 1964. 
19. Hamlin, R. L., R. Jackson, J. Himes, F. S. Pipers, 
and A. Townsend. Electrocardiogram of the bottle- 
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21. Redding, R. W. The spread of the excitation wave 
in the ovine left ventricle. Ph.D. Dissertation, Ohio 
State Univ., Columbus, Ohio, 1957. 
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ventricle. Abst. 32nd Scientific Sessions, Am Heart 
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26. Hill, J. D. The significance of foreleg position in 
the interpretation of electrocardiograms and vector- 
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27. Hill, J. D. A correlative study of spontaneous right 
ventricular conduction disturbance in the dog. 
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93, 1961. 
29. Douglas, S. D. Correlation between the surface 
electrocardiogram and air sac morphology in the 
white leghorn rooster. Am. J. Physiol. 199:355, 
1960. 
