HEART FIELD OPERATIC3N 



299 



Presumptive 

 Blood Cells 



Intestine 



Esophagus, 

 Stomach 



Liver 



Heart 

 Blastopore 



Location of presumptive heart material in Ambly- 

 stoma. A, Organ-forming areas mapped on the 

 ventral portion of an opened gastrula, dorsal view; 

 B, gastrtda, lateral view; C, neunUa, stage 15, 

 right lateral view; D, stage 22. Heart-forming 

 areas on C and D are outlined by broken line; 



E, transverse section at level of arrow in D; 



F, enlargement of ventral portion of same section. 

 (A and B, redrawn after Holtfreter, '38: C, re- 

 drawn after Bacon, '45. ) 



[i^|^?^^j?:^M^:^?^^-'?%^-:- ■■'.^•■^■■''^^Wi 



Heart -^v..&^| 

 forming V.^^^^'? 



,<_■ ./ 



Mesoderm '^^ll-^^^f^^^^nf^^ll^' 

 Entoderm — ■ — ' '^IS':'-:^! ^^;;|-i^p 



(Courtesy W. M. Copenhaver and 

 W. B. Saunders Pub. Co. from 

 Willier, Weiss, and Hamburger 

 "Analysis of Development". 

 1955.) 



large mass of ecto-mesoderm. From a slightly older embryo outline and remove an 

 area of similar shape, and including ecto- and mesoderm, but from the presumptive 

 hind-limb region. Transplant this mass to the operated (host) embryo wound area, hold 

 it in place for 30 minutes or more, and when healed, return the embryo to normal cul- 

 ture medium. (See Ekman, 1925. ) 



TRANSPLANTATION OF HEART FORMING AREAS 



Early stages: In Anuran stage #17 or Urodele stage #25, the heart forming mesenchyme 

 from the bilateral sides have fused ventrally. Remove a rectangular piece of ventral 

 ectoderm along with all available adherent and underlying mesoderm, and transplant it 

 as one piece to the flank region of a second embryo, previously prepared. The second 

 (host) embryo should be slightly younger than the donor. Such a transplanted heart anlage 

 should give rise to a tubular heart of four typical parts, with its own pulsations but with- 

 out any circulatory elements. 



Late stages: Use Anura stage #19 or Urodela stage #34 to #38 where the heart is well 

 formed. Anesthetize the embryo in freshly made MS 222 (1/3, 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 above), it will show clearly the persistence of function in 

 the absence of innervation. 



