572 



Upon the Motion of the Mammalian Heart. 



A contraction wave following the spiral muscle bands, bands arranged to 

 wring the blood powerfully from the heart, would tear them asunder, 

 would rupture the fragile vessels penetrating all at right angles. 



Gaskell, with that acuity of perception which was his pronounced 

 quality, thought of the muscles of the sinus and of auriculo-ventricular 

 ring as primitive remnants, highly endowed as is the primitive cardiac 

 tube with the function of rhythmicity, poorly endowed with the function 

 of conductivity ; he associated the fine structure of the tissue of the rings 

 with peculiarity of function, A similar but more complex relation between 

 structure and function is to be demonstrated in the striated tissues of the 

 mammalian heart. Rhythmicity as a function is most highly developed 

 in the sino-auricular and auriculo-ventricular nodes, structures which 

 closely resemble each other in the fine details of their construction, 

 structures which are now both held to represent remnants of, or develop- 

 ments of, the original sino-auricular ring. Conductivity is a function held 

 in varying degree by the mammalian tissues. The Purkinje cells are the 

 largest striated cells, and possess the highest content of the carbohydrate 

 glycogen ; they conduct most rapidly. The fibres of the auriculo-ventricular 

 node, the smallest to be found in the heart, conduct most slowly (15) ; they 

 are almost devoid of glycogen. Between these two extremes are the fibres 

 which compose the walls of the auricle and ventricle. These fibres are 

 of intermediate size, the content of glycogen is intermediate, the power 

 of conduction is intermediate. The ventricular fibres are said to contain 

 less glycogen than the auricular (2), they also conduct less rapidly. Thus, 

 the rate at which the wave flows is controlled by the structure and chemical 

 constitution of the tissues through which it passes ; the musculature in its 

 various parts is so differentiated that from its appearance the manner of 

 its working may be known. 



REFERENCES. 



1. Bayliss and Starling, ' Journ. of Anat. and Physiol.,' vol. 9, p. 256 (1892). 



2. Berblinger, 'Beitrage z. pathol. Anat. u. allg. Pathol.,' vol. 53, p. 207 (1912). 



3. Cohn and Trendelenburg, 'Archiv f. d. ges. Physiol.,' vol. 131, p. 1 (1910). 



4. Einthoven, ' Archiv f. d. ges. Physiol.,' vol. 130, p. 287 (1909). 



5. Erlanger, 'Journ. Exper. Med.,' vol. 8, p. 50 (1906); see also 'Heart,' vol. 1, p. 177 



(1909). 



6. Eyster and Meek, ' Archives of Internal Medicine,' vol. 18, p. 775 (1916). 



7. Flack, 'Journ. of Physiol.,' vol. 41, p. 64 (1910). 



8. Ganter and Zahn, ' Zentralbl. f. Physiol.,' vol. 25, p. 782 (1911); 'Archiv f. d. ges. 



Physiol.,' vol. 145, p. 335 (1912). 



9. Gaskell, 'Journ. of Physiol.,' vol. 4, p. 43 (1883) ; 'Phil. Trans.,' 1882 



