ON VACCINATION 119 



return to the status quo ante takes place, accompanied or 

 preceded by the appearance at the point or points of 

 entrance, but now of exit, of a more or less well-defined 

 vesicular spot or spots, which indicate the exanthematous 

 nature of the morbid process thus artificially produced. 



In the imbibition of the virus, one, two, or all of these 

 channels must have been used or entered in the process, 

 viz. the haemal lymph, the blood, or the nervine lymph 

 circulatory channels. If the haemal lymph channel had 

 been the one used, then we would have expected that the 

 solution of continuity of the vascular walls involved would 

 have been made good or closed by the vis medicatrix 

 nature before a process of regurgitation, were that pos- 

 sible, and exudation could have ensued after the processes 

 of absorption and incubation had been run ; in like 

 manner and for like reasons the same may be said of the 

 blood channels, besides, it might be mentioned that the 

 walls of the haemal lymph and blood capillary vessels are 

 made up of organised structures which are eminently 

 prone to heal, and, hence, would have prevented the occur- 

 rence of "eruptive" exudation. We are, therefore, 

 reduced to the necessity of entertaining and maintaining 

 the opinion that the vaccine virus enters the system by 

 the nervine lymph circulation, that it invades and multi- 

 plies in the fluid with which that system is inter-penetrated 

 and surrounded, and that, on the cessation of the morbid 

 processes set up there, a small quantity of the tainted 

 fluid or culture, as it might be called, is extravasated at 

 the still open or thinned walls of the originally traumatised 

 nerve terminals, which do not circulate further, but excrete 

 their contents there. 



Vaccinia, and consequently variola, are, therefore, dis- 

 eases primarily of the nervous system, and it is through 

 the impression made and left on that system by the 

 artificial, or natural, effects of their respective viri that 

 immunity or protection is conferred ; but no doubt the 

 secondary effects of these diseases are experienced through- 

 out the whole organism, non-nervous as well as nervous. 



Were it possible to analyse the changes wrought in the 

 minute structure of the skin involved in the vaccine 

 trauma and succeeding vesiculation, we are convinced that 



