THE ARGUMENT FROM DISEASE 159 



the body. The truth appears to be, then, that both germ- 

 cells and somatic cells, however capable of injury in other 

 particulars, are exceedingly stable in their hereditary tend- 

 encies. Were the germ-cells not stable the species could 

 not persist ; were the somatic cells not stable the individual 

 could not persist. Even when cells are exposed to injury so 

 severe that many perish, the survivors still retain their 

 ancestral traits. 



264 It is widely believed by alienists, that various dis- 

 eased conditions, especially phthisis, are causes of " mental 

 instability" in offspring. It is possible of course that 

 phthisical people may have an undue proportion of mentally 

 unstable children, but even so it would not necessarily follow 

 that parental phthisis is the cause of filial instability. The 

 weakness against phthisis is specific, but it is well known 

 that all causes which physically depress the individual increase 

 the liability to infection. It is known also that similar causes 

 tend to create mental instability. Parents tend to transmit 

 inborn characters to offspring. A defective constitution, 

 therefore, might expose one generation to phthisis and result 

 in the next in mental instability. But in that case the filial 

 instability would not be due to the parental phthisis. It does 

 not appear, however, that statistics have been published 

 which demonstrate that the children of the phthisical are 

 more liable to mental instability than the children of the 

 non-phthisical. Alienists have noted merely that many of 

 the inmates of lunatic asylums, who, speaking generally, are 

 drawn from a very poor class much exposed to disease, have 

 a phthisical ancestry, a fact which may be noted of many 

 people, especially those of the same class, outside the walls. 

 Nor has it been shown that races which have been longest and 

 most afflicted by phthisis, for example the English and the 

 Lowland Scots, are mentally less stable than races that have 

 been less afflicted, for example the Terra del Fuegians and 

 the Highland Scots. Moreover of late years the prevalence of 

 phthisis has greatly decreased, whereas that of insanity has 

 enormously increased. Were the former the cause of the 

 latter the exact opposite should be the case. 



265. In his very interesting and valuable address to the 

 Zoological Section of the British Association, Professor J. 

 Cossar Ewart insisted that " there is a considerable amount 

 of evidence in support of the view that changes in any part 

 of the body or soma which affect the general welfare influence 

 the germ-cells." He added 



266. " It may first be asked, Does disease, in as far as it 



