BY E. M. JOHNSTON, F.L.S. 27 



in itself to rise or fall during each period is more probably 

 referable to some hidden cosmical influence. 



Thus there are probably three great causes operating, as 

 regard the variations of Typhoid, viz : — 1. Local hygiene; 2. 

 Seasonal influence; 3. Cosmical influence. None of which 

 may be neglected in forming a correct opinion from local 

 death-rate data. 



The Influence of Cosmical or Obscure Causes, such 

 AS Epidemics, in Adding to or Varying the 

 Intensity of Local Causes of Disease Over Wide 

 Cycles of Years. 



If we study the diagram showing the movement of the 

 death-rate in Australia and Europe since 1850, we at once 

 perceive a series of waves generally covering a period of ten 

 to eleven years. These are somewhat modified in different 

 countries by what we may term subordinate ripples upon the 

 greater wave, but these in no way disturb the close agreement 

 of the greater waves, or cycles. The length and the time 

 occupied by each great cycle closely correspond with the sun- 

 spot periodicity. 



There can be no doubt of the marked agreement of the 

 disturbance of the general death-rate of the various Colonies 

 in Australasia, each of which differs in the actual death-rate 

 relative to their respective populations. It becomes a most 

 important question, then, to enquire whether and how far these 

 wave-like disturbances — not the relative local death-rate 

 peculiar to each place — are within the limits of human control, 

 and, therefore, to what extent are they of value as an 

 indication of local sanitary conditions ? 



The cause of this periodic rise and fall in the death-rate 

 occurring simultaneously in different widely separated 

 countries is, I admit, a most difficult question. It is open to 

 ■us to consider the results as due 



1. To human neglect of, or attention to, sanitary conditions 



fluctuating simultaneously in different countries, in 

 accordance with the periodic fluctuations of the 

 death-rate. 



2. To periodic fluctuations in the intensity of specific zymotic 



diseases in centres where they are endemic — but 

 periodically becoming epidemic or pandemic when the 

 period of intensity is at its height. 



3. To periodic fluctuation in the medium or channels of 



conductibility from endemic centres, the death-rate 

 decreasing with the increase in non-conductibility and 

 increasing with its increased powers of conductibility. 



4. To hidden cosmical influences simultaneously affecting the 



life and activity of disease germs throughout wide 



