JULT 19, 1912] 



SCIENCE 



91 



These experiments Lave shown that the newly 

 grown, cellular syncytia and the isolated single 

 heart muscle cell can become functionally ac- 

 tive, beating with a rhythm similar to that of 

 the intact heart. 



Pieces of the hearts of chick-embryos of all 

 ages and of young hatched chickens were 

 used. A growth of tissue, composed almost 

 entirely of muscle cells, occurred from all 

 pieces when suspended in the media of both 

 types of cultures, (1) the ordinary hanging 

 drop culture (the plasma modification'-) of 

 the method of Harrison^ and (2) a large modi- 

 fied type of culture. This apparatus is so ar- 

 ranged as to supply the tissues continuously 

 with fresh media and to wash away the waste 

 products without in any way disturbing the 

 growing cells. I described this method in de- 

 tail before the American Association of 

 Anatomists, December 2Y, 1911.2 Serum was 

 used as the fluid medium in the latter type of 

 culture. 



Rhythmical activity of the newly grown 

 cells was noted in 3 out of 15 of the large 

 type of cultures (No. 2), and in 2 out of 150 

 of the ordinary hanging drop cultures. These 

 cells were located definitely within the clot 

 and had a clear cytoplasm which contained 

 very few fat droplets. The rhythmical activ- 

 ity did not occur during the active outwander- 

 ing of the cells but, later, after they became 

 permanently located in a definite portion of 

 the clot and were undergoing slow multipli- 

 cation and differentiation. In one culture 

 rhythm occurred as early as the fifth day, 

 while in others as late as the fourteenth day 

 of the life of the culture. The greater num- 

 ber of positive results in the large type of 

 culture (No. 2) can be associated with the ac- 

 tive and continuous growth of the tissue 

 over a sufficient period of time. Active 

 growth and a regular rhythm has been ob- 

 served in these cultures for 30 days, while in 

 the hanging drop culture the active growth 

 and the regular rhythm cease after the third 

 or fourth day. The growth then becomes 



"Harrison, E. G., 1907, Froc. Soc. Exp. Biol, 

 and Med., 140; 1910, Jmr. Exp. Zool, Vol. 9, 

 787. 



gradually less and the rhythm intermittent, 

 ceasing entirely after 10 or 18 days unless the 

 tissue is transferred to a new medium. The 

 method of repeated transplantation from the 

 culture to a new medium has not as yet been 

 sufficiently developed to allow any increase 

 in the life and the activity of the newly grown 

 cells. At each transfer of the tissue the ac- 

 tively growing and multiplying cells are de- 

 stroyed and a new growth takes place from 

 those more latently active cells in or about the 

 tissue mass. 



The original pieces of heart muscle trans- 

 planted to a tissue culture vary as to their 

 rhythmical activity in relation to the portion 

 of the heart from which they are taken as well 

 as the age of the embryo. Pieces of the 

 auricle, especially of that part situated near 

 the entrance of the veins, taken from embryos 

 of all ages and from young hatched chickens, 

 beat when suspended in plasma. The pieces 

 of the ventricle do not beat when taken from 

 embryos older than 10 days, unless special 

 methods of preparation and treatment are 

 used. 



Ehythmically beating cells have been grown 

 from the contracting pieces of the hearts of 

 young embryos and from one piece of the ven- 

 tricle of a fourteen-day chick embryo. The 

 absence of movement in the original mass of 

 tissue of this culture facilitated greatly the 

 study of the delicate contractions of the newly 

 grown cells. The syncytial network which 

 surrounded the original tissue and one isolated 

 cell were beating rhythmically. This cell was 

 situated far out in the clear medium away from 

 all other tissues and beat with a rhythm inde- 

 pendent in phase from that of the syncytium. 

 The rate of all beating cells in this culture was 

 the same, 50 to 120 per minute, or a rhythm 

 typical for rhythmical beating pieces of ven- 

 tricular muscle. 



The experiments show: (1) that the cells 

 which have grown and differentiated in a tis- 

 sue culture can later assume their character- 

 istic function; (2) that rhythmical contrac- 

 tion similar to that observed in the embryonic 

 heart can occur in an isolated and single heart 

 muscle cell; (3) that the rhythmically con- 



