ACTION OF THE HEART. 299 



the systole and diastole of the Ventricles, but the division is very unequal as 

 regards the Auricles; about one-fifth of the whole being occupied in their 

 contraction, and the remainder being taken up by their dilatation. 1 The 

 following tabular view will perhaps make the relations of the. several parts 

 of this series more intelligible: 



AURICLES. VENTRICLES. 



4 f Dilatation. Contraction. 



5 \ Continued Dilatation. First stage of Dilatation, 



^ Contraction. Second stae of Dilatation. 



In some very careful experiments, Bonders 2 ascertained that in different per- 

 sons in whom, when at rest, the pulse varied from 74 to 94 per minute, the 

 duration of the systole of the ventricles, i. e., from the commencement of the 

 first to the commencement of the second sound varied from 0.327 to 0.301 

 of a second, and that it constituted from 40.6 to 45.6 per cent, of the time 

 occupied by an entire cardiac revolution. In a man whose pulse was only 

 32 per minute, the duration of the ventricular action was still 0.307 to 0.325 

 of a second, though its proportion to the whole revolution had fallen to about 

 18 per cent. From whence it appears that the duration of the activity of 

 the Ventricles, determined by the ganglia of the heart itself, is independent 

 of the duration of the entire cardiac revolution, which is regulated by the 

 Pneumogastrics. 3 The systole and diastole of the heart are represented in 

 Figs. 120, 121 (p. 300). 4 An entire cardiac revolution may be described in 

 the following terms, commencing with the systole or contraction. The Auri- 

 cles and Ventricles are both filled with blood, which has flowed into them from 

 the veins. The Auriculo-ventrieular valves are open, and the arterial valves 

 (both aortic and pulmonary) are perfectly closed. A sudden contraction of 

 the Auricles now takes place, commencing at the entrance of the great veins, 

 and extending, without appreciable pause, over the ventricles. By the con- 

 traction of the Auricles a portion of their contained blood is discharged into 



1 See Marey, Circulation du Sang, Paris, 1863, p. 68. 



2 Nederlandsch Archiefvoor Genees- en Natuur-kunde, 1866, p. 139, of which paper 

 a full translation is to be found in the Dub. Quart. Journ., vol. xlv, p. 225. See also 

 some estimates by Landois, Henle and Meissner's Bericht, 1866, p. 411. 



3 See Sibson, Medical Anatomy, 1869, and the instructive papers by Dr. Haiford, 

 now Prof, of Physiology at the Univ. of Melbourne, On the Times and Manner of 

 the Closure of the Auriculo-Ventricular Valves, and On the Movements and Sounds 

 of the Heart, Lond., 1861 ; also Pettigrew's Lectures on the Physiology of the Cir- 

 culation, Edin. Med. Journ., 1873. 



4 The outlines of the cavities of the heart, and the great vessels, are here indicated, 

 at the end of the systole of the heart, by continuous lines at the end of the diastole by 

 interrupted or dotted lines. (The drawing and descriptions are taken from Dr. Sib- 

 son's admirable treatise on Medical Anatomy, 1869, Col. 73. The dotted lines are 

 less accurate than the interrupted lines.) The systolic movements are everywhere 

 shown by arrows, the extent of the movements being marked by the length of the 

 arrows. As it is more difficult to watch and measure the movements of the heart 

 from the side than from the front, the side view (Fig. 2) is not so accurate as the 

 front view (Fig. 1). Briicke (Vorlesungen, 1874, p. 172), whose experiments were 

 made by implanting needles into the hearts of rabbits, and watching the reversed 

 motions of the heads, maintains that all parts of the ventricles move downwards in 

 systole with the exception of the apex, the amount of movement increasing from be- 

 low upwards. Haiford (op. cit.) believes the apex of the heart is drawn up towards 

 the base, but nevertheless undergoes less change of position than any other part, its 

 upward movement being neutralized by the descent of the whole heart occasioned by 

 the elastic recoil of the great vessels springing from the base. A condition of active 

 dilatation has been admitted by many writers; there seems reason to believe that 

 what gives rise to this impression is partly occasioned by the injection of the coronary 

 arteries. See A. H. Garrod in Nature, Feb. 19th, 1874. 



