126 HUMAN LONGEVITY. 



from races and nations, where large averages cancel more 

 or less completely all subordinate inequalities, to the lesser 

 divisions of families and local or limited communities, where 

 new causes come into action, no longer neutralising each 

 other in their general results. All who rightly comprehend 

 the law of averages will see at once that this must be so. It 

 is impossible to particularise the many causes which affect 

 the health and life of man in various localities ; but the 

 subject of longevity in families connects itself with one of 

 the most curious questions in human physiology that of 

 the hereditary transmission of physical qualities and pecu- 

 liarities from parents to offspring. Every one is familiar 

 with this fact in the case of other animals ; especially in those 

 domesticated by man, and made more useful to him by the 

 varieties thus produced. We cannot affirm that the capacity 

 for change by such hereditary transmission, is as great in 

 man himself; for except in the instance of the gigantic 

 Prussian grenadiers, and possibly in the usages of some 

 savage tribes, we are not aware of any attempt distinctly 

 made to test this question. But in one form or other the 

 fact is familiar to the observation of all ; subject, indeed, to 

 the anomalies which beset every part of this great mystery ; 

 yet exhibited in such numberless ways, on mind as well as 

 body, as to show its mighty influence on the destinies of 

 man. The most minute peculiarities of external feature, as 

 well as the grosser conditions of stature and bulk, are capa- 

 ble of being thus transmitted ; and we cannot doubt, upon 

 pathological observation, that the internal organs also 

 possibly even that wonderful fluid which circulates through 

 and ministers to all of them are subject to the same in- 

 fluence derived from one generation to another. The bearing 

 of this influence on the formation of national diversities of 

 feature and character, is a most curious collateral topic, but 

 its discussion would be out of place here. 



