132 
JANE I. KOBERTSON. 
the internal structures. The sinu-auricular aperture is indicated by 
an arrow that is seen against the pulmonary fold. 
Fig. 2. — Drawing of the heart from the left side, magnified about 3^ 
times. The left walls of the left auricle, ventricle and bulbus cordis 
have been removed. The opening of the pulmonary vein (P.F.) into 
the left auricle is indicated by an arrow, as is also that of the Imlbus 
from the ventricle (F. B. o.). 
Fig. 3. — Drawing of the j)i'Oximal segment of the bulbus cordis, 
magnified about 5 times. The dorsal wall has been cut open a little to 
the right of the middle line, so that the dorsal row of vestigial valves 
has been divided unequally. No part of the bulbus wall has been 
removed. 
Fig. 4. — Drawing of the bulbus cordis from the ventricular side 
magnified about 34 times. Tlie ventral wall of the bulbus has been 
removed in the distal and transverse segment. 
Fig. 5. — Drawing of the heart (magnified about 50 times) about 
.Stage 31. The transverse position of the heart is still distinct. 
Fig. 6. — Drawing of heart (magnified about 50 times) about Stage 
33. Owing to the various growth adjustments the transverse position 
of the heart is rapidly being lost. 
Fig. 7. — Drawing of heart (magnified about 50 times) about Stage 35. 
The position of the heart is now practically that of the adult condition. 
