1908] on The Present Phase of the Tuberculosis Problem. 287 



In this connection Professor Karl Pearson has recently, as the 

 result of his own researches, arrived at the conclusion that " a theory 

 of infection does not account for all the facts." 



The careful and sustained investigations as, for instance, of Niven, 

 and other observers, demonstrate, it would seem, that under certain 

 circumstances of overcrowd iug, and prolonged exposure to mass 

 infection, the disease possesses a considerable degree of personal 

 infectivity. The evidence adduced under this head is what I have 

 termed that of " association," i.e. persons who have developed the 

 disease have been shown to have been previously associated with 

 persons suffering either from recognised or suspected phthisis, and 

 these associations have been regarded as those of effect and cause. 



There are, however, two not impossible explanations of these 

 occurrences. One, that they are cases of recent independent infection, 

 the other, that they are cases of the re-awakening of old foci of 

 infection, concerning the enormous prevalence of which more will 

 be said directly. Moreover, all who have had experience of tracing 

 the history of the onset of pulmonary tuberculosis recognise the 

 enormous difficulty of the task, which was drawn attention to long 

 since by Portal and Buhl, and, as Dr. West observes, experience in 

 investigations of this nature indicates that — 



The date of the original infection with tubercle is thrust further 

 and further back — even, it may be, into early childhood ; so that in 

 considering the causation of phthisis it will be necessary to deal with 

 the original sources of infection in early life. 



It has been suggested that the term " conditionally infectious " is 

 one which might be applied to phthisis, and seeing that this term 

 implies that if the conditions which are thought to induce infection 

 are avoided, infection is unlikely to ensue, the term may perhaps be 

 employed as embodying a helpful working hypothesis. 



The Difficulty of dealing' Administratively w^ith 

 Consumption as with Smallpox. 



As definite proposals have been made to deal with a chronic 

 disease such as consumption, in like manner to an acute disease such 

 as smallpox, it will serve a useful purpose to indicate some of the 

 social effects which might result. 



Cases of smallpox are at once notified, removed to a fever hospital, 

 and kept there until recovery or death ensues — one or other of which 

 events occurs, as a rule, within six weeks. Those who have been in 

 contact witli the patients are kept under observation, or actually in 

 quarantine at the expense of the rates, for a fortnight ; children from 

 the same house are kept from school, and, at times, associated adults 

 are kept from work. After the removal of the patient to hospital, the 



