cxliv THE BEGINNINGS OF LIFE. 



others have suggested, they are probably more strictly de- 

 pendent upon individual states than upon external con- 

 ditions, and consequently are more baffling to those who 

 attempt to fathom their causes. Measles, scarlet fever, and 

 small-pox, are undoubtedly amongst the most contagious 

 of diseases, and therefore the chances are always strongly 

 in favour of their contagious origin in any given case. But 

 should this satisfy us ? Should we be content to say that 

 even measles, .scarlet fever, and small-pox, are propagable 

 only by means of contagion, and cannot arise de novo 1 ? 

 Are they not strictly comparable with many other general 

 infectious diseases which undoubtedly arise ' spontaneously ' ? 

 Do we not see amongst those which may so arise that 

 the degree of contagiousness is altogether variable ? Does 

 not this seem to increase gradually in each affection, as 

 the off-cast particles tend to undergo molecular changes, 

 which are more and more capable of initiating chemical 

 actions of a spreading character in the blood, or mucous 



1 It seems to me that at present the facts are looked at much too 

 exclusively from one point of view. It is fully admitted by many per- 

 sons that during epidemics, more especially, a large number of cases of 

 small-pox occur, even in isolated situations, in which it is quite impos- 

 sible to obtain any evidence of contagion. When we consider further 

 that the disease is epidemic at times, and then almost dies out, although 

 multitudes remain who might be infected, we must admit that something 

 besides contagion is undoubtedly operative in facilitating its spread 

 during these times, and therefore we may assume it to be possible that 

 this ' epidemic influence ' of itself might, in certain persons, suffice to 

 engender the disease without contagion. Dr. Gavin Milroy (loc. cit.) 

 says : ' This most interesting subject has not been investigated with that 

 patient and searching care which all physical problems demand. The 

 prevailing negative belief rests on merely presumptive grounds, rather 

 than on sifting inquiry. That outbreaks of measles, hooping-cough, etc.. 

 have been observed in various remote islands, and at distant intervals of 

 time, without any traceable connexion with previous cases, either in the 

 country itself or amongst recent arrivals, can scarcely be doubted. 

 Hillary particularly alludes to his having noticed such occurrences in 

 Barbadoes ; and the medical history of other West India islands would 

 afford, I believe, similar evidence.' (See also Hecker's ' Epidemics,' 

 pp. 215-218.) 



