HEART F lELD OPERATIONS 



507 



b. Late etagea : Use Anura stage #19 or Urodela stage #5i+ to #58 where the heart la 

 well formed. Anesthetize the embiyo in freshly made MS 222 (l/5,000 in operating medium) 

 and graft (transplant) the entire heart mass^ plus liver and foregut, to the flank region 

 of an embryo of the same age or one stage younger. While this operation will not demon- 

 strate self-differentiation (as In "a"), it will show clearly the persistence of function 

 In the absence of innervation. 



CULTURE OF HEART TISSUE IN ISOLATION 



After the bilateral heart rudiments have fused ventrally it is possible to remove the 

 mesodermal mass and the overlying ectoderm, and to have It differentiate in isolation In 

 the appropriate medium. In general (see "Isolation Culture" exercise) the culture medium 

 should conalst of the normal culture medium which contains some (coelomlc) body fluids 

 from adults of the same species. In addition, it la now known that 0.5% sodium sulfa- 

 diazine will retard the development of bacteria and hence prolong the life of the Isolate. 



25 



HEART f^y^t 

 ARE/ 



AMBLYSTOMA 



4TH BR. CLEFT 



OPTIC VESICLE 



SENSE PLATE 



TRAPEZOID AREA 

 HEART AREA 



GILL ANLAGE 



PRONEPHRIC AREA 



RANA PIPIENS « STAGE 15 



31 /^ 31 



HEART 

 AREA 



MANDIBULAR ARCH 



The explanted heart may be cultured in a hanging drop of medium, on the underside of 

 a coverslip sealed over a depression slide; In Standard Solution in a depression slide; or 

 over an agar- embryonic fluid base. If the medium is changed every 5 to 1)- days, the ex- 

 plant may be carried to quite an advanced atage of differentiation. 



