278 Dr. H. T. Bulstrode [May 15, 



the bacillus, in 1882, there has been, it would seem, a tendency to 

 concentrate attention almost exclusively on the parasite or bacillus, 

 an attitude which, as certain administrative work based entirely 

 upon this view has already shown, is not unlikely to lead to dis- 

 appointment. The actual position cannot be better set forth than in 

 the words of Professor Osier, who possesses a remarkable aptitude for 

 clothing scientific ideas in the attractive garments of antiquity. 



There are tissues in which the bacilli are in all probability 

 killed at once — the seed has fallen by the wayside. There are others, 

 again, in which a lodgment is gained and more or less damage done; 

 but finally the day is with the conservative protecting forces — the 

 seed has fallen upon stony ground. There are tissue soils in which 

 the bacilli grow luxuriantly, caseation and softening, not limitation, 

 and sclerosis prevail, and the day is with the invader — the seed has 

 fallen upon good ground. 



The importance of this soil " resistance " has not in the past been 

 sufficiently appreciated, and it is not inconceivable that it may in the 

 relatively near future come to be regarded as the major factor in the 

 tuberculosis problem. 



Evidence indicating the significance of this soil factor is forth- 

 coming from the experimental data of the Royal Commission on 

 Tuberculosis, wherein it has been shown that it is not the absolute 

 number of l)acilli which supplies the determining factor, but the dose 

 in relation to the susceptibility of the auimal. Bacilli from the 

 same source may give rise to general progressive tuberculosis in one 

 animal and to a limited retrogressive tuberculosis in another. 



It is important, however, to observe that a sufficiently large dose 

 will usually overcome all resistance. 



Illustration of procHvity to the disease may also be seen in the 

 frequency with which tuberculosis of the joints or bones follows 

 some injury, and tuberculosis of the lungs some damaging afi'ec- 

 tion of those organs, while the tendency of the disease to attack at 

 one age period the joints, bones and glands, and at another the lungs, 

 betokens, perhaps, different tissue proclivities at different ages. 



Sanatorium treatment aims less at the direct destruction of the 

 bacillus, than at the promotion of such a condition of the " soil " 

 as shall prove hostile to the life of the parasite, and tuberculosis 

 treatment based upon opsonic index values must seemingly be regarded 

 as directed towards the same end. Finally, as will be seen presently, 

 the post-mortem records of persons who have died of other diseases, 

 or been accidentally killed, show conclusively that only a proportion 

 of all existing cases of tuberculosis are recognised during life, so that 

 in the vast majority of infected persons the resistance of the body 

 has overcome the onslaught of the bacillus. 



It is difficult, if not impossible, to procure really reliable data as 

 to the susceptibility or resistance of different races of man, but there 

 is some evidence pointing towards the conclusion that such obtains. 



