io THE MECHANISM OF THE CIRCULATION. 



the auricle. Above, its surface is multicouvex (Fig. 3), while below it is 

 multiconcave. Beneath the concave surface a quantity of blood is 

 perceptible, which is not expelled by the ventricular systole. The 

 chordae tendrnese which are inserted on the edges of the flaps are 

 shorter than those attached to the under surface. 1 



Hesse 2 measured the base of the heart in both the state of diastole and 

 in the systole produced by heat-rigor. In the latter state he found the 

 diameter of the base of the heart was much diminished. 



If this diminution takes place in the systole of the living heart, it must not 

 only aid in the closing of the auriculo-ventricular orifice, but must increase 

 the sacculation of the valvular diaphragm. Chauveau 3 was, however, by 

 the insertion of his fingers in the heart of the horse, not able to detect 

 any very great diminution of the basal diameter. Sibson 4 has likewise 

 denied any marked diminution of the diameter of the auriculo-ventricular 

 orifice. 



The condition of heat-rigor produced by Hesse is very different to that 

 which obtains in the normal systole, and the observations on the living heart 

 must be accepted as of far greater worth. 



Many views have been held as to the action of the papillary 

 muscles. Among such are the following : — 



1. That they approximate the flaps of the valves and aid in their 

 closure ; 



2. That they open the valves, because they are the last to receive 

 the wave of contraction, and therefore continue to shorten after the 

 rest of the ventricle has passed into diastole ; 



3. That synchronously with the systole of the ventricle they 

 contract, and, in proportion as the longitudinal axis of the ventricular 

 cavity shortens, pull in the slack chords tendinea j , and thus prevent the 

 valves from being forced too far into the auricles. 



An attempt has been made by Eoy and Adami to record the time of 

 action of the papillary muscles, by passing a wire hook through the 

 auricle, and this they hooked on to a flap of the mitral valve. The 

 hook they connected to their myocardiograph (see p. 39). The con- 

 traction of the ventricular wall was simultaneously recorded. From 

 the records thus obtained, these authors concluded that the con- 

 traction of the papillary muscles began later and ended earlier than 

 that of the ventricular wall, and in the proportion of 5 to 8. 5 The 

 movement of the flap of the valve is rapid at first, and afterwards 

 reaches a maximum somewhat slowly ; this maximum is maintained 

 for a brief space, and is followed by a sudden relaxation. 



Fenwick and Overend, 6 Haycraf t and Paterson, 7 have directly recorded 

 the contraction of the papillary muscles in the excised heart. In order to 

 effect this, the heart is with the greatest rapidity cut out and laid open, 

 the base of a papillary muscle is then pinned down to the table, 

 while hooks are attached to the apex of the muscle, and to the 

 ventricular wall. These hooks are connected by threads to writing 



^rehl, Arch.f. Physiol., Leipzig 1889, S. 290. 

 "Arch./. Anat. u. Entweklngsgesch., Leipzig, 1880, S. 344. 

 3 Loe. cit. 4 " Medical Anatomy," 1869, p. SO. 



5 Roy and Adami, Practitioner, London, 1890, vol. xliv. pp. 88-94. 



6 Brit. Med. Joum., London, 1891, vol. i. p. 1117. 



7 Joum. Physiol., Cambridge and London, 1896, vol. xix. p. 262. 



