TMI i . 555 



1 > y 1 1 A i i i . 1-68 a 



.striking form. >incr- it- t\\.. Li- ral walls develop large 'ings 



free edges of 



tin- latter, which in addition soon acquire notches, IIP 



ward, and >ul>MM|u'nt ly enfold more .. 



heart, th<- truncu- ai terio -' ml a part of the surface of 



ventricle, 



Tin- auricular ca : 



narrowed place in t h.- eardia bube Owing bo 'ho great flattening 



of its endot I.elial tulx* in ' .!> almost 



Fig. 805. 



Fig. 305. -Heart of A human embryo, the body of which w, 

 II pare fig. 313.] 



: uiu -us arteriosns ; K, venoiu end of the S-*hpej cardiac me. 



lig. 306. -Heart of a human embryo that waa 4 3 mm. long. otk mtiurment (onbryo Bl), 



Mincus arti-riosus ; ok, caiialis auricuUiru ; iA, atiiiun with the h<art-OTtifiig 

 ho (auriculae cordu). 



coming into contact, the passage between U T 



n-ducrd to a narrow tr:m>\vrM- fissure. It is here that the atrio- 

 'ricular valves are afterward- l-vel'je<L 



of tli. Mum. presents the form of a 



curved tube (figs. 305, 306 A), which however soon changes 

 1 MI a1 i \eiy < aily period th. -re is observable on its anterior [ventral] 

 and posterior sttrfaoei .1 diattoi I'irrow running from above d^ 

 \\ard. tli. /-it (6g. 307*' allows a left 



and a right halt' of the \vntricle to I* 'iy. The 



latter is the narmw. r. .nd m i upward into the truncus 



artei ginning "f which is >oniwhat enlarged 



