mi: OBOAHI Off mi: IN 



; { 



d m 



I 





Fig. 299. Three diagrams to 

 illustrate the formation of 

 the heart in the Chick. 







.1-tliclial sacs of the 



i!>tht-li;ii HM ..f the heart ; 

 ch, i-h.Tihi ; M, body- 



;. iniui 



I*rietal 



im.i.llr 



nii.M'. in tin- 



tin' i ..f tl.- 



!oj>ci ; i/i. in- 



testinal suture, in which 



till' t\VO lilt. 



fused ; (^6, part of the onto- 



. hil'll l.:i.S IHV..IIH- (!-- 



in-d from the t'liitlit-liuni 



of the i-qiuulK 



the intestine at the intes- 



tinal suture and lies on 



the yolk ; -f- dorsal nieso- 



cardium ; ventral meso- 



cardiuiu. 

 A, Ihe youngest stage .-I. 



tJ,,- infolding of tueapl..: 



n-.p!. ui.'.bynieansof whnli 

 



te*t: 



011;: folds 



the iial sacs of 



have been esta- 



blished between the 



germ-layer and the visceral 



lllelnyer. 

 S, s ler stag*. 



The two folds (A 'if) hate 



IK.-I in i h<- intestinal suture 



thelial sacs of the heart 

 '.mo below the 



^'Ut. 



list stage. The part of 

 i-a whu-li lines 

 Mi- !.,M : .: ; i )hasbeoom 

 M-i>:kr:it<-<l -it tli-- ;;.r.---.in I 

 suture (B dn) from the re* 

 m.i: the ento- 



. \\hii-h (M) lies ; . 

 tli- >..!k. -i.v Mi.- kwotfl -,.. ,1 o., ,,f thr heart are in contact ; they 



M a cardiac suYiicnsorium formed by the visceral middle layers, the 

 !.:. ii .!,. . tonal 1 and aa under part aesocardUsa 



int. i uis (" }. \\y means of this mesocardium the priniiUve body-cavity is teuputarily divided 

 ii^> tn 



Mi' A ,!H 





on 

 (+> and 



35 



