AS TO THE HEREDITY OP ACQUIRED CONDITIONS. 451 



mining in all cases whether a given defect belongs to it or to one of 

 the other divisions. This group may be divided into the following 

 classes: — (1) Clefts of various kinds, due to the presence of 

 tumours or to fluids consequent upon inflammation. Certain 

 forms of cleft-palate belong to the former category, abdominal 

 and spina clefts to tbe latter. (2) Deficiencies of extremities 

 &c. due to inflammation of tissues leading to formation of fibrous 

 tissue, its contraction, and the strangulation of growing parts. 

 As examples of this may be named certain forms of peromelia 

 and (?) atresia ani. (3) Deficiencies due to amniotic pressure. 

 (4) Deficiencies due to adhesions of the amnion &c., including the 

 so-called intra-uterine amputations. Having thus very briefly 

 sketched the main lines of classification, it will be necessary in 

 the next section, as each malformation comes up for examination, 

 to consider at greater length and in more detail its special 

 etiology. 



Section II. — Nature oe Hereditary Maleormations. 



Intliis section I purpose examining those malformations whose 

 hereditary nature is established, seriatim. In connection with the 

 etiology of each will be considered its nature, whether blasto- 

 genic or somatogenic. I shall have to draw largely from a former 

 paper of my own "On Congenital Malformations and Heredity" *, 

 in which are collected a number of recorded cases of such mal- 

 formations, but without reference to their etiology. It will be 

 convenient in the subsequent part of this paper to group the 

 malformations under the classes which have been indicated in the 

 first section. 



Part 1. — llalformations hy Excess. 



The most important members of this group, all the forms, that 

 is, of double monstrosity, have to be entirely excluded from the 

 present inquiry. An enormous majority are non-viable, or only 

 maintain a separate existence for a few liours or days ; and the 

 remainder are, even if married, sterile. The same remark applies, 

 as will appear later, to most of the major and even to some of 

 the minor forms of abnormality. "We can, however, with profit 

 examine two classes of cases not commonly grouped under the 



* Proc. Birrn. Phil. Soc. vol. vi. pt. 1, 



32* 



