i5 



inherited, and their relative proportions preserved; whilst in 

 some families the heart and great blood-vessels are found 

 naturally large, in others comparatively small. The relative 

 size of the brain, and other peculiarities of the nervous 

 system, are indisputably transmitted from parents to children; 

 and that certain families are characterised by a plethora or 

 paucity of blood, or of bile, is a matter too well known to 

 require further consideration. 



What physicians denominate as idiosyncrasies are very 

 frequently, if not invariably, inherited ; and that what have 

 been termed the "subordinate" in contradistinction to the 

 " dominant characteristics " are hereditarily transmissible is 

 proved by the well-known facts as to fecundity and longevity 

 which often characterise families for many generations. Just 

 as some families are distinguished by the hereditary trans- 

 mission of longevity, so may others be characterised by 

 short duration of life, as strikingly exemplified in one 

 generation after another. There are other cases of a still 

 more interesting character where, from one generation to 

 another, the members of certain families seldom, if ever, 

 survive after a certain age. To this class of cases belong 

 also the many instances of premature bodily and mental 

 decay to which some families are subject as the result of 

 heredity the exemption, or comparative immunity shared 

 by other families as to the influence of certain contagious 

 diseases, and the increased susceptibility of others : and 

 that muscular strength and special skill in certain physical 

 exercises are hereditarily transmitted is a fact as well known 

 now as in early times ; also lisping, stammering, shrillness 

 and gruffness of the voice, nasal intonation, and loquacity. 



That acquired modifications are also transmissible there 

 can be no doubt ; and amongst these, perhaps, none more 



