THE FORM OF THE HEART. 5 



This method of investigation is open to considerable fallacy. The hearts 

 are excised and unsupported by surrounding structures, and while the diastole 

 is artificially produced by a high injection pressure, the systolic contraction is 

 not normally obtained, for, contrary to the natural systole, it takes place against 

 no resistance. Thus it comes about that the great contraction of the auriculo- 

 ventricular orifices, found by Ludwig in the rigored heart, is not confirmed by 

 observations on the living heart. Eecently Haycraft and Paterson have cut 

 a series of sections through the frozen thorax of dogs, after the heart has been 

 fixed either in diastole or systole. 1 From these sections the form of the heart 

 has been reconstructed. The great difficulty is to obtain the death of the 

 animal with the heart in either the true diastolic or systolic shape. Death 

 nearly always takes place with the heart in diastole, but, according to the 

 distribution of the blood at the moment of death, the heart may be dilated 

 more or less. To obtain death with the heart in systole is a matter of con- 

 siderable difficulty. Haycraft and Paterson obtained the best results by the 

 injection of a solution of corrosive sublimate into the jugular vein. 



R. 



A. B. 



FIG. 1. Sections through the frozen thorax of a dog. A, Heart in diastolic death ; 

 B, In systolic death. Haycraft and Paterson. 



In the figure are presented the appearances observed in sections from 

 two dogs, and seen from below. In A the heart is in diastolic death, and 

 in B in systolic death. 



In a third figure these authors illustrate the alteration in the position 

 of the heart produced by placing the animal after death on the left side. 

 The heart has fallen over to the left, and has, while compressing the left 

 lung, expanded the right. This illustrates the interaction of the thoracic 

 organs on one another; by merely altering the position of the body, and 

 thus of the heart, air may be driven out of one lung and sucked into the 

 other. 



By taking plaster casts of the interior, after fixing the heart in diastole 

 or systole, Ludwig and Hesse studied the form of the ventricular cavity. As 

 to the accuracy of this method, the same reservations must be made as above. 

 In diastole the cavity of the left ventricle forms a short and wide tube, while 

 the auriculo-ventricular opening is separated from the aortic orifice by the 

 pendulous anterior flap of the mitral valve. In heat-rigor, a condition of 

 contraction greater no doubt than that produced by any systole during life, the 

 cavity appears as a narrow slit which is star-shaped in the region of the 



1 Haycraft and Paterson, Journ. PhysioL, Cambridge and London, 1896, vol. xix. 

 p. 496. 



