in the Fatus of Vcrtebrated Anhnuls. 317 



form the auricular appendages. Their parietes become covered 

 with numerous small irregular marks, which appear to indicate 

 the formation of the fleshy pillars, (Fig. 23). 



From late observations, it would appear that the division of 

 the ventricle commences some time before that of the auricle. 

 Malpighi was also acquainted with this change in the ven- 

 tricle ; but as he had observed the bulb of the aorta, in im- 

 mediate connexion with the great arteries, to become slight- 

 ly swollen at its root on the fourth day, he was led to sup- 

 pose that this cavity formed the left ventricle of the heart ; 

 and he erroneously concluded that the ventricle first produced 

 must have been the right. Haller having with care investi- 

 gated this subject, detected the error of Malpighi, and satisfied 

 himself that no part of the bulb of the aorta was converted into 

 the new ventricle, but that this part remained to form the roots 

 of the great arteries springing from the heart. He thus de- 

 scribes the appearances of the right ventricle * : '< Hora fere 96, 

 sive die exeunte quarto, prima vestigia novi accrescentis ventri- 

 culi adparent. Sub bulbo nempe aortas tuberculum nascitur, 

 multo corde brevius, perinde rubellum, ovatuni, quod in prin- 

 cipio suo superius videtur, et vero ventriculo transversum insi- 

 det. Recte taraen adhibitis oculis adparet, eum ventriculum 

 qui hactenus solus fuit, suo semper loco manere immutatum et 

 sinisterius solum conspici, dexterius vero mucronem solum te- 

 nere, dum novus ventriculus ipsi imponi videtur, quia brevior 

 est, nee attingit mucronem." 



It will appear, however, from what we are going to relate, 

 that Haller, though correct in his description of the appearances 

 which presented themselves, had observed the right ventricle 

 only when it was nearly completely formed. Professors Ro- 

 lando and Baer have, since the time of Haller, investigated this 

 subject, and have traced the commencement of the right ventri- 

 cle to a much earlier period than any previous observers ; but 

 their accounts of the mode in which this cavity is produced dif- 

 fer considerably from one another. 



According to Rolando f , the right ventricle is produced by 



• Opera INIinora, vol. ii. p. 376. 



t Siir la Formation du Coeur, &c. Journ. Complement, torn. xv. & xvi. 



