882 TRANS ACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



August, twelve men had gone to Stack an Armin to catch 

 gannets, and as there were not enough men left on the 

 island to man a boat to take them off, they were left on 

 Stack an Armin all the winter, and were only relieved 

 when the Factor's boat came the following summer. That 

 they were able to support themselves in such a place says 

 much for their hardihood, but they were put to great 

 straits, and had it not been that one of their number had 

 a rusty nail with him, which being fashioned into the 

 shape of a fish-hook, enabled them to catch fish after the 

 birds had left, they could hardly have survived. As it 

 happened, however, they undoubtedly owed their lives to 

 being left in this position of isolation. The island was 

 repeopled almost entirely from the survivors, the 

 Fergusons being the only family which has settled in the 

 island since that time. The frightful mortality 

 experienced in that epidemic shows very clearly what 

 smallpox is capable of when it breaks out in a community 

 unprotected either by vaccination or by previous 

 experience of the disease. In all civilized communities 

 which have been in contact with certain diseases for 

 numbers of generations, a process of continual selection as 

 regards those diseases has been, and is, going on, the 

 individuals which are most susceptible to those diseases 

 dying" oif, and the race being* continually recruited from 

 those who are most resistant to them. But an isolated 

 community like that of the St. Kildans, not having under- 

 gone any such weeding-out process, the members of it 

 present a virgin soil for the growth of the bacilli, which 

 initiate the various infective disorders, and these diseases 

 are hence apt under such circumstances to assume an 

 unusual virulence. If a disease such as measles were 

 ever imported into St. Kilda. it is to be apprehended that 

 the -rate of mortality from it would he a high one, 



