I III 



60 into intimate . I envelop* 



each one of them with a SJKHM. here urine 



in tin- spongy \\all of the ventii. u.-d \\ith 



cndothe'.ium, which t"\vard tin- nufftOQ - ' i't <*nd blindh 



which communicate with the central cavity ami like thin receive 

 them the stream of blood. 



The eml>r\onic i. mala resembles in its first 



condition that which has I * en described tip to this point -the heart 

 (*t the lowest Vertebrates, the Fishes. In the former as in the 

 latter it ooosisti "f a region, the atrium, eeiven the venous 



Mood from the Ixdy. anl of another, tin- which <lrives the 



I into the arterial vessels. Corresponding to this cor 

 t he 1 ion in embryos of this stage and in Fishes 



// K simjJ'' and a single one. This becomes changed in 



evolution of Vertehrates. as in the eml.r\ cnic life 



/, upon the appearance or 



!>f ii"j of the heart an ' <>/ tl t . /,/.,.. duced. 



The cause of such a change is clear, from the topographical reli 

 f (!<>' tii-n Imnj* to the faart, the formei 'he immediate 



vicinity of the heart ly e\ auinat i..n ,.\ i he t'.'ie-gut (fig. 314 Iff). 

 The lunu r - t h.'i-.-ioff i-.-^.-iN.- th.-ir l>Io<ui from an 

 very near the heart, from the fifth [>ixth] pair of aortic arches that 



from the truncii> .> -.milarly they ^r: 



\enous pulmonary llool dii throu-i 'ems, 



the puluionai-y \t-in-, which, originally ir 



trunk (1'iouN. i .-n into the ., . of the great 



us trunk-. Therefore the blood that flow* >tt of the heart 



ftack again to the heu, in it 



; <* cornea into 



f the bixly currents are separated Jrom 

 i/tout the short coune of ike 



VOKH >ich both traverse in coin ventricle, 



and truiu-u> arteri< 



The process of separation l..-_'in> in t he \vriehrate phy \\i\n 

 l>ipnoi and Amphil.ia. in which pulmonary respii 

 tin' iirM time and supplant> lro: 



Vertel.r.-i- lOOOmplished dun; lopuient. 



Therefore we now have to f.-ll,.\\ ..ui hoH -i-h. 



in the case of Mammal- and exp t . ( -ially of Man, according to the 

 recent investigationa of Hn, - are 



formed how atrium and ventricle are *;. uto right and 



