CONTAGIOUS MATTER. 





to the blood and tissues, it increases to such an extent 

 that in many cases sufficient is produced in one sub- 

 ject to infect hundreds of persons, the population of a 

 town, or even a whole country. 



The infecting matter has been supposed by some 

 to consist of some subtle entity, which was not 

 cognizable by the senses, or to be made evident in 

 any way. By others it has been considered to be 

 matter in a gaseous state. Great authorities have 

 defined it, with apparent precision, to be a chemical 

 body, which may exist as a volatile vapour,* in a 

 solid state, or dissolved in fluid. With a still more 

 decided appearance of precision, the contagious poi-" 

 son has been pronounced to be an albuminoid matter 

 in a state of rapid chemical change, which has not 

 yet been isolated. Thus, the Cattle Plague Commis- 

 sioners expressed the opinion that the poison of 

 that highly contagious malady was probably matter 

 " of a kind which is, and always will be, undiscover- 

 able by the microscope." They remark " that 



* The view that some contagious poisons are volatile seems to have 

 been adopted because it has been found that the disease could be pro- 

 pagated through air and by the breath of the affected man or animal, 

 but such a conclusion is unjustifiable, for, as is well known, par- 

 ticles as large as starch globules can be wafted from place to place by 

 currents of air, and these are not volatile. Moreover, multitudes of 

 insoluble particles, of determinate size, always exist, buoyed up by the 

 ordinary air on the surface of the earth. But solid particles should not 

 be called volatile unless they can be converted into vapour which, by 

 condensation, again assumes the general form and state the particles 

 first exhibited. 



B 2 



