2XCUBA.TIQN PERIOD. 



107 



as absorption of toxins, are facilitated. This would 

 seem to find special application in cholera and 

 bacillary dysentery. In cholera general invasion 

 of the body by the living organisms does not take 

 place, although the intestinal surface is denuded 

 to a greater or Jess degree. The vibrios penetrate 

 to a certain rather superficial depth, where they 

 appear to become dissolved, and with their dissolu- 

 tion, poisons, in addition to those which were pre- 

 viously secreted, are set free. The conditions are 

 similar in dysentery. 



To summarize, micro-organisms gain entrance to 

 the subjacent tissues through wounds, by means of 

 their own power of injuring the surface and grow- 

 ing into and through it, and probably also through 

 the agency of inwandering leucocytes. Phagocytic 

 epithelial cells in some instances may play a part, 

 but this is hypothetical. Toxins are absorbed for 

 the most part through surfaces which have been 

 previously injured, but some of them are able to 

 pass through previously healthy mucous mem- 

 branes. 



The term incubation period signifies the inter- 

 val between the first introduction of a pathogenic 

 micro-organism, or its toxin, until the develop- 

 ment of the first symptoms which characterize the 

 onset of the disease. In many infections, as in 

 typhoid fever, a feeling of malaise, headache and 

 nausea, frequently appear a few days before marked 

 symptoms develop, and this period is called the 

 prodromal stage. It may be considered either as 

 the latter end of the incubation period, or as the 

 beginning of actual "onset/ 3 



The length of the incubation period varies 

 greatly in different infections. In cholera it may 



summary. 



Incubation 

 Period. 



