34 ,6 Sir Everard Home on the changes the egg undergoes 
had begun to enclose the areolar covering of the yelk, and a 
pulsation was distinctly seen in the trunk that supplied the 
vesicular bag with blood. The pulsations were 79 in a mi- 
nute while the embryo was kept in the temperature of 105°, 
but when the temperature was diminished the pulsation 
ceased, and when restored was reproduced. The pulsation 
was kept up, by attention being paid to the temperature, for 
36 hours. Muscular action had become vigorous in the limbs. 
When the embryo was completely immersed, although the 
temperature of the water was 108°, the pulsations immedi- 
ately ceased, the blood being no longer aerated. Plate 
XXXVI. fig. 7, 8, 9. 
In 8 days , the anastomosing branches of the vesicular cir- 
culation had the arterial pulsation very strong in them. Plate 
XXXVII. fig. 1,2,3. 
In 9 days , the vesicle had nearly enclosed the yelk, but not 
intirely ; for when the embryo was turned upon its back, and 
the opposite surface examined, a portion of yelk was unen- 
closed, and beyond it some of the albumen was met with not 
mixed with the yelk. Plate XXXVII. fig. 4, 5, 6. 
In 10 days, the vesicle was opened, and the upper half 
turned aside. When the amnion, which had become full of 
water, was opened and the embryo taken out, the thorax was 
found completely enclosed ; the roots of the feathers were 
distinct, and the passage for the areolar as well as the vesi- 
cular vessels exposed. 
In 14 days , the yelk remained out of the body. When the 
thorax and abdomen were opened, and the heart as well as 
the lobes of the liver turned aside, the trunks of the blood- 
vessels could be traced to the heart ; but as the arteries 
