VITAL rRlNCJl'JLK. 37 



not assume the leaf of the rose ; nor did the stamens of the 

 rose change into the petals of the meadowsweet. In no 

 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, concretions of hair, and even teeth 

 have been found ; substances which, in ordinary cases, are 

 fabricated in the uterus ; and all 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 occur on different parts of 

 the body, 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 ROBERT SIBBALD f. 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 BAILIE'S " Account of a Change of Structure in the Human Ova- 

 rium." Phil. Trans. 1789, vol, Ixxix. p. 71-78. 



f " Scotia Illustrata," tab. xi. fig. 23. part i. p. 60. 



