!68 ENTRANCE OF DISEASE 



hospital, if cases of disease depending upon conta- 

 gious poisons are also admitted. It is probable that 

 if cases of surgical operations were placed in buildings 

 apart from medical cases, the mortality from pyaemia 

 and allied diseases, would be considerably reduced. 



State of Vessels favouring the Entrance of Disease- 

 germs. Admitting, then, that it has been proved 

 that contagious poisons generally consist of minute 

 particles of living matter or bioplasm, and that this 

 living matter, to produce its characteristic effects 

 upon the system, must enter the blood, let us inquire 

 how the living particles gain an entrance into the 

 vascular system in cases in which no wound is made, 

 in which there is no solution of continuity in any 

 part of the vascular walls. The fact that, of a number 

 of persons equally exposed to the influence of con- 

 tagium, some will contract the disease, while the 

 majority will escape, may be accounted for by sup- 

 posing either that in the latter case the particles do 

 not really penetrate the vascular wall at all, or that, 

 they are in some way destroyed as soon as they 

 traverse the wall of the capillary and come into 

 contact with the blood. 



We must therefore enquire what circumstances 

 would favour or assist the passage of the living particles 

 of the contagious material througrrthe vascular mem- 

 brane into the blood. Thin- walled capillary vessels, as 

 is well known, come very near to the free surface in 

 many parts of the body, and if these capillaries are 



