542 CIRCULATION OF BLOOD AND LYMPH. 



upon its side it flattens in diastole so as to increase in length, 

 and systole causes a shortening. If the heart is held or placed 

 with its apex pointing upward it flattens during diastole so as 

 to shorten the diameter from base to apex and during systole 

 this diameter is lengthened. In ourselves the exact change of 

 shape is probably different in the erect from what it is in the 

 recumbent posture. Speaking generally, the accounts agree in 

 stating that the long diameter of the heart is decreased, base and 

 apex are brought closer together, and the diameter from right to 

 left is also decreased, while the anteroposterior or ventrodorsal 

 diameter is increased. That is, the outline of the base of the heart 

 during diastole is an ellipse with its short diameter in the ventro- 

 dorsal direction. During systole this outhne approaches that of a 

 circle. A more interesting change is described for the apex of 

 the ventricle. Owing to the whorl made by the superficial fibers 

 at this point as they turn to pass into the interior (see Fig. 223), 

 the systole causes a rotation of the apex, which is thereby 

 forced more firmly against the chest wall. This rotation and 

 erection of the apex during systole may be seen upon the exposed 

 heart of the lower mammals and has been described also for man 

 in cases in which the heart is covered only by the skin, owing to 

 malformation in the chest wall (ectopia cordis) or to surgical 

 operations. The exact position and size of the heart in man and 

 its variations in these respects under various normal and patho- 

 logical conditions may be studied quite successfully by means of 

 the x-rays. When the x-rays are passed through the chest, the 

 heart forms a shadow which may be seen with the aid of the fluor- 

 escent screen and which may also be photographed. The appa- 

 ratus used for this purpose may be so arranged that the rays pass 

 through the chest in parallel lines and give a shadow of the exact 

 size of the heart. The arrangement of apparatus for this purpose 

 is designated usually as an orthodiagraph, and the photographic 

 record obtained is spoken of as an orthodiagram. It may be shown 

 by this means, for example, that during muscular exercise there is 

 an increase in the size of the heart owing to the greater venous 

 inflow, while at the end of exercise, with the cessation of respira- 

 tory and muscular activity, the heart becomes smaller than normal, 

 owing to the fact that the faster rate, which is maintained for a 

 while, causes the heart to empty itself more rapidly than it is filled.* 

 The Apex Beat. — ^The apex of the heart rests against the chest 

 wall at the fourth or fifth intercostal space, and here the systole 

 may be seen and felt in consequence of a slight protrusion of the 

 wall. Much discussion has ensued as to why this protrusion 

 occurs during systole, since the apex is drawn toward the base 

 and the volume of the heart is diminished by the output of 



* Nicolai and Zuntz, "Berliner klin. Wochenschrift," No. 18, 1914. 



