On a Case of Abnormality hi the Htman Foetus, 421 
built of birch twigs, and lined with down, and was appa-» 
rently the work of the bird itself, and not the old one of any 
other bird. Instances of wild ducks occasionally using the 
nests of other birds, have been observed, and even at as 
great a height as thirty feet from the ground. In these in- 
stances, it is believed, the young birds are brought down to 
the ground by the bill of the motheio 
II. Note on a case of Ahnormality in the Ossification of the Parietal 
Bones in the Human Foetus. By R. H. Traquair, M.D. 
Some time ago I dissected the head of a human foetus of 
between the eighth and ninth months, in which the parietal 
bones presented a condition apparently at variance with the 
well-known rule, that these bones are two in number, and 
each developed from a single ossific centre. 
In this cranium the parietal bone of the left side is per- 
fectly normal, being ossified from one centre, which corres- 
ponds with the well-marked parietal eminence. 
On the right side, however, the part which represents the 
parietal bone is divided into two distinct pieces, in a line ex- 
tending from the middle of its posterior margin obliquely 
forwards to a little above its anterior inferior angle. Of 
these two pieces, each of which is of course ossified from its 
own centre, the lower is accordingly somewhat triangular, 
and is equal in size to one-half the upper rudely quadran- 
gular part; and the two pieces form together a double 
parietal bone, which is larger by about one-fourth than the 
single bone of the opposite side. 
This cranium is therefore abnormal—- 
1. In possessing three parietal bones instead of two. 
2. In the asymmetrical disposition of these bones, two 
being on one side, one on the other. 
3. The vault of the cranium is also asymmetrical in this 
respect, that the double parietal bone of the right side is 
considerably larger than the single one of the left. 
The only other analogous case of which I am at present 
aware, is one recorded by Yon Sommering.* He has de- 
* Ticdemann und Treviranus Zeitschrift fiir Physiologie, ii. 1826. 
