very small. The unfit have been steadil}^ eliminated 

 through successive generations : the more resistive 

 are with us yet. 



Pigeons show this even more markedh', as would 

 only be natural seeing that their domestication has 

 existed even longer than that of the Fowl. Passing 

 by the distinct reference to them in Genesis xv. 9 

 (date about 1900 B.C.), we find them mentioned during 

 the fifth Eg3'ptian dynast3% about 3000 B.C., as 

 already existing in a domesticated condition."^" And 

 as we find that from the earliest times there has 

 always been practised in connection with them a 

 more or less rigid system of artificial selection, 

 necessitating the keeping of them in large numbers, 

 and since both Pliny and Juvenal speak of their being 

 kept in " cock-lofts " on the tops of the houses, we 

 know that their housing must always have been 

 characterized b}^ overcrowding and general insanita- 

 tion. A curious confirmation of the principles attach- 

 ing to racial immunities is to be found in the fact that 

 even now the prevalence of a wet season, and more 

 especially the presence of a non-waterproof covering 

 to the Pigeon house, will bring about a few septicaemic 

 cases in studs of Pigeons that otherwise remain free 

 for years in succession. Their quarters have always 

 been more or less drier than those devoted to poultry, 

 and hence they cannot even yet altogether withstand 

 the septic bacillus when it is invigorated by the 

 presence of moisture. 



There remains yet to be mentioned a form of 

 immunity which we may call sporadic, i.e. attaching 

 to individuals apart from any question of any racial 

 immunity in which they might or might not have the 

 chance of participating. This sporadic immunity, 

 which has been alluded to in various connections in 



•Darwin. Plants and Animals tinder Domesticaiion, 2ud Edit., page 21.4. 



