68 PROTOPLASM 



used are those from the chick embryo. The culture medium is 

 one prepared to meet the particular requirements of the tissue. 

 The receptacle should permit microscopic study. Either a 

 depression (hollow-ground) slide or a Carrel flask will serve 



Fig. 52. — Culture chambers; right, hollow-ground slide; left, a Carrel flask. 



(Fig. 52). Suitable tissue is to be had in the chick embryo, 

 preferably eight to ten days of age (Fig. 53), though any age and 

 other animal embryos and adults serve well. The nature of 

 the experiment determines the kind of tissue to be used. A 

 typical experiment would proceed as follows: A five- to ten-day 

 chick embryo is removed from the shell (Fig. 54) and placed in 



a watch glass containing some saline solu- 

 tion. The chick heart is isolated and cut 

 into numerous tiny pieces. One of these bits 

 is placed either in a Carrel flask or on a 

 cover slip in a suitable amount of culture 

 medium (Fig. 55). If a cover slip is used, it 

 is then inverted and sealed on a depression 

 slide (Fig. 52) or placed on a vaseline ring 

 made on an ordinary slide (Fig. 55). The 

 flask or slide is then placed in a constant- 

 FiG. 53.-A seven-day temperature oven at 37.5°C. and allowed to 



chick embryo. 



incubate. Within several hours or a day, 

 cells will have migrated out from the tissue, forming a fringe of 

 very loosely joined cells around the so-called explant (Fig. 56). 

 If the explant is a bit of heart tissue, it may, even though it is 

 but a twentieth part of the original organ, continue beating for 

 many days after isolation. It is one indication, of which there 

 are many, that the culture is alive and normal. More extra- 

 ordinary is the observation of W. H. Lewis of a single cell of the 

 chick heart in culture which pulsated with the same rhythm of 



