t>2 Sir Everard Home on corpora lutea. 
years old, and the corpus luteum represented in the engraving 
is that of a first calf. [[Plate VI. fig. 4; and Plate VII. fig. 2, 
and g.[] In the hog tribe, the age of puberty is six months ; 
and in the series of drawings of their ovaria, one is given from 
a sow pig at four months, in which no corpora lutea had begun 
to appear. [Plate VIII. fig. 2. [] In another, between five and 
six months, several have made a considerable advance, [Plate 
VIII. fig. 4-[l and in one nearly six months they were com- 
pletely formed, and their cavities filled with blood, similar 
to the human corpus luteum containing the ovum, but no ova 
were detected. [[Plate VIII. fig. 6.[] 
In another virgin pig, nearly six months old, Mr. Bauer 
was so fortunate as to meet with corpora lutea in the very act 
of bursting to part with their ova : the appearance is shown in 
Plate IX. fig. 1 and 2. From this most fortunate occurrence 
we learn that animals part with their eggs whether there is sex- 
ual intercourse or not, and this is done with such force, that the 
cavity of the corpus luteum is absolutely inverted, so that the 
ovum is exposed completely to the emission of the male. The 
extravasation of blood in rupturing the ovarium, and invert- 
ing the corpus luteum, is in many instances so great, that 
some of it passes out through the vagina, which when met 
with, is considered a sign of impregnation having taken 
place. As soon as the ovum is expelled, the corpus luteum 
recovers itself, and returns to its natural state. When the 
ovum accidentally adheres by a portion of the chorion to the 
inner surface of the corpus luteum, as is shown to be the case 
in Plate III. fig. 4, it may retain its hold; and however com- 
pleat its expulsion, may be carried back, and form what is 
