VITAL PRINCIPLE. BY 
not assume the leaf of the rose; nor did the stamens -of the 
rose change into the petals of the meadowsweet. Inno 
case is there a mixture of the character of other species. 
Each preserves, amidst its greatest changes, that individua- 
lity of constitution by which its vital principle is distinguish- 
ed. 
In animals, monstrosities of a similar kind prevail. Thus 
in the human ovarium, coneretions of hair, and even teeth 
have been found; substances which, in erdinary cases, are 
fabricated in the uterus; and ail this in the absence of sexual 
intercourse *. 
In many parts.of the human body, encysted tumors have 
been observed, covered internally with skin, producing 
hairs. ‘That such organs have assumed the functions of the 
skin, is obvious from the portions of detached cuticle and 
hairs found in the cyst, which have been thrown off in suc- 
cession. In these instances, which occur in other animals 
as well as man, the hair corresponds, in appearance, with 
that which grows upon other parts of the body. Hence 
when -encysted tumors of this kind form in sheep, they 
contain wool. ‘Tumors likewise oceur on different parts of 
the bedy, producing horny excrescences. A figure -of a 
production of this kind, cut from the head of a woman:in 
Edinburgh, in 1671, and deposited in the Library of the 
College, is given by Sir Ropers Sispanp +. Similar in- 
stances have occurred in England, and other countries. 
Although usually termed Horns, they are essentially diffe- 
rent from the armature of the ruminating quadrupeds. 
They have no core upon which they have been formed ; 
consequently they are destitute of a central cavity. They 

* Dr Bariie’s “ Account of a Change of Structure in the Human Ova- 
rium.”—Phil. Trans. 1789, vol. Ixxix. p. 71.-78. 
+ “¢ Scotia Illustrata,” tab. xi. fig. 23. part i. p. 60. 
