280 Dr. E. T. Bulstrode [May 15, 1908] 



with animal and vegetable species the history of which can be read 

 in geological formations, so with the disease-producing but perishable 

 vegetable micro-organisms, there has been a period when they 

 evolved and devolved, or when, from some sudden change, they dis- 

 appeared within a short space of time. All we are in a position to 

 say is, that in Europe within historical times certain diseases, such 

 as plague, leprosy, typhus fever and relapsing fever, have apparently 

 almost disappeared, and this without any very direct attack by the 

 ingenuity of man, and, as will be seen shortly, there are indications 

 that in this country the same natural law, if it be one, may be 

 operating to promote the fading away of tuberculosis. 



The devolution of certain diseases is probably due in the main to 

 unsuitable environment brought about l)y improved social conditions, 

 but it is a matter of doubt whether, in the case of diseases such as 

 leprosy and syphilis, the factors of both progressive immunity of the 

 host and exhaustion of the parasite, have not played a material part. 



The Behaviour of Pulmonary Tuberculosis (Phthisis) in 

 England and Wales since the Middle of the last 

 Century. 



In order to clearly apprehend the tuberculosis problem, it is 

 essential to appreciate the manner in which pulmonary tuberculosis 

 has behaved in the entire absence of any direct or conscious measures 

 taken against it ; in the absence, that is to say, of a belief that the 

 disease was, as is now believed, communicable from person to person, 

 or that its prevalence was seriously amenable to direct control. 



With the view of bringing out this point, there is here reproduced 

 from the official sources of the Registrar-General a chart showing the 

 manner in which the disease in question has steadily declined over 

 practically the whole period to which the chart relates, and it may be 

 said that until quite the close of the last century no conscious 

 measures which could in any way have influenced the figures for the 

 country as a whole were being taken. Since then certain measures — 

 such as notification, education by visits of inspectors as to control of 

 sputum and wholesome living, disinfection of houses, and the erection 

 of sanatoria — have been introduced ; but, although such measures 

 have no doubt exercised a beneficial effect in localities where they 

 have been practised, they have not, as yet, been of sufficiently general 

 character to exercise any detectable influence upon the behaviour 

 of a curve representing the death-rate for the whole country. 



It is desirable also to bring out the fact that the remarkable 

 fall indicated in Chart I. has been participated in by practically 

 every county in England and Wales, and by North and South Wales, 

 and for this purpose Chart II. is introduced. It will be noted that 

 the top of the black coloration indicates the death-rate in each 

 county for 1871-80 ; the top of the double cross-hatching that for 

 1881-90 ; the top of the single cross-hatching that for 1891-1900. 



