CONTINUOUS INVASION. 97 



through the wall of the intestines. The bacillus 

 itself is believed not to proliferate in the intes- 

 tines. The condition is one of intoxication with- 

 out true infection. 



In some of the intestinal diseases the cavity of continuous 



,-,.,,. J Invasion 



the intestines appears to act as a sort of reservoir from a 

 in which the organisms proliferate to an unlimited 

 degree, and from which they reach the circulation 

 more or less continuously in large numbers, either 

 in a living or dead condition. This relates particu- 

 larly to typhoid, paratyphoid, cholera and dysen- 

 tery. They are primarily surface infections. In 

 the two former, however, the organisms, during 

 the early days of infection, reach the circulation in 

 a living condition in large numbers, and may even 

 proliferate in this situation. In cholera, the vibrios 

 show a disposition to general invasion, but appear 

 to be killed off before they have actually pene- 

 trated the intestinal wall. The same condition 

 probably prevails in bacillary dysentery. It is the 

 general belief that the intoxication in these 

 instances comes about through the disintegration 

 of the micro-organisms, as a consequence of which 

 a poisonous protoplasm is set free. This conception 

 has its origin from the facts that it has been diffi- 

 cult or impossible to obtain potent soluble toxins 

 in culture media, and that the bodies of the killed 

 organisms are sufficiently toxic to explain the 

 intoxication. Eecent work, however, indicates that 

 a certain quantity of toxin may be produced in arti- 

 ficial cultivation, and it is possible that the condi- 

 tions in the body are much more favorable for Ohronl 

 toxin production than are artificial surroundings. 

 Certain chronic infections, even when they involve 

 deeper tissues and internal organs, show from the 



