180 



Thf Iragiiunls ol" heart wcrt* oblaiiu'd Iroin chicken em- 

 bryos aboul M to 10 tlays ohi. In some cx|)(i-imcnls Ihc Irag- 

 menls belonged to dillerenl embryos and in some tliey were 

 derived trom llie sanu' hearl. whilst in oilier experinienls 

 two traj*menls derived ti'om the same hearl and Iheir cut 

 edgt's brought into close proximily. This was done in 

 Ihe lollowing way. A relatively large ti-agment of heart was 

 placed in llie cuilnre medium, and while the cullure medium 

 was in Ihe licpiid slate, the IVagmenl was divided by a 

 clean cut and kept together by means of a needle and the 

 point ot the cataract knile until coagulation of the cullure 

 medium look place. I'sually three fragments of heart were 

 placed in one culture, two adjacent each other and one 

 separate which served as a control. 



Soon after the cultures were prepared, the contractions 

 of the respective heart fragments were checked, l^'or each 

 of the three fragments, the intervals of time between two 

 contractions were measured by means of a stop-watch. After 

 12 honis incubalion the cultures were again examined and 

 the contractions checked, 12 hours later the same thing was 

 repeated and so on. 



When several fragments of lieart tissue wei'e embedded 

 in the same culture medium, not two of them pulsated in 

 the same way. The individual fragments were able to pulsate 

 exactly in the same waj' for long periods of time, when 

 everything else was constant. In the experiments wliere the 

 distance between tlie two adjacent fragments was about one 

 mm., the zone between the fragments were filled up witli 

 the outgrowth of filjrolilasts from the pieces. In a few ex- 

 periments of this kind, it was observed tliat the individual 

 contraction of the two adjacent fragments was not regular 

 any longer, after the fibroblasts had intermingled in the zone 

 between the fragments, (table 19). Befoi'e, the contractions 

 were very regular, i. e. tlie intermission was the same foi' 

 the same fragment for a long period of time. l)ul after the 

 outgrowth of fibroblasts had uniled. the contractions became 



