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arities which predispose to them. Sometimes, indeed, the 

 hereditary predisposition is so patent (as frequently seen in 

 pulmonary and brain affections) that, notwithstanding the 

 fact of every effort being made to prevent it, the disease 

 becomes fully developed ; and, just as in physiological 

 heredity, certain characters or peculiarities remain latent 

 during an intermediate generation, so also the potency of 

 atavism or reversional heredity is frequently seen to influence 

 similarly the phenomena of disease. I shall, however, refer 

 to this question more in detail in the course of these papers. 

 Predisposition is also setal, or connected with the age of 

 individuals, and is most remarkably displayed in infancy for 

 the following reasons : The skin and mucous membranes of 

 infants are remarkably delicate ; they are characterised by a 

 high degree of sensibility or capacity of sensation, also of 

 contractility or capacity of contraction : the size of the 

 head is large in proportion to that of the body : they are 

 exposed to the irritation of dentition ; and they have little 

 power in maintaining the external heat. After the first 

 dentition to the sixth or seventh year is a period of great 

 excitement of the nervous and vascular systems, and 

 characterised by a predisposition to febrile and inflammatory 

 affections, also to those of an exanthematous character. 

 From this up to the age of puberty a period of comparative 

 health the eruptive or exanthematous predisposition con- 

 tinues, to which may be added a liability to epistaxis, and r 

 at puberty, those constitutional derangements especially 

 affecting females, in connection with their uterine functions 

 and allied conditions. From puberty to manhood twenty- 

 four or twenty- five years of age is a dangerous period, 

 usually characterised by a strong predisposition to tubercular 

 and scrofulous diseases, haemorrhages, and digestive dis- 



