296 TEXT-BOOK OF BACTERIOLOGY. 



matter by various means again get into the digestive canal of pre- 

 viously healthy people. The drinking-water also (as Almquist has 

 recently rendered very probable), the milk, soiled linen, unclean 

 fingers, etc., are the welcome bridge on which they step over the 

 chasm from the first individual to the second and infect the latter, 

 if he is otherwise susceptible, i.e., " individually predisposed." We 

 shall by no means dispute the possibility of this mode of transmis- 

 sion being promoted or obstructed lay temporal and local influences. 



The bacilli having once been received, they penetrate into the 

 intestine itself by passing the stomach. They settle in the intes- 

 tinal wall, begin there their pernicious activity, and gradually find 

 access, by means of the lymph current, to the lymphatic glands, 

 first the mesenteric and then the remote ones. They then get back 

 into the blood and are distributed over the organs, preferring 

 spleen and liver. They never get from the placenta of pregnant 

 women to the foetus a fact established by Eberth and several other 

 investigators. 



Efforts have been made to trace the typhus bacilli in the blood 

 of living persons in order to discover directly the course of their 

 distribution. These have been successful in a few cases, but the 

 procedure has not led to positive results and did not therefore 

 recommend itself for diagnostic purposes. 



The morbid changes are developed most distinctly in the intes- 

 tine, and these are so decidedly important for typhoid fever that 

 they have given the name to the disease (enteric fever). In the 

 ileum and upper caecum a decided swelling of the solitary follicles 

 and Peyer's patches is found; on'the surface of the latter necrotic 

 scabs are formed which slough and leave typhoid ulcers behind. 

 The mesenteric glands and the spleen are also regularly enlarged ; 

 the other organs, the liver and kidneys, however, remain macro- 

 scopically nearly unchanged. We can find the bacilli at all these 

 different places only by the aid of the microscope, and frequently 

 they can only be determined with difficulty. 



We already know that the typhus bacilli are very sensitive to 

 decoloration and readily lose the coloring substance a fact natu- 

 rally becoming more prominent in treating sections than in cover- 

 glass preparations. It is best to leave the sections for twenty-four 

 hours in Loffler's solution, to wash and decolor them in simple 

 water, to dehydrate them in anilin oil, dry them on the slide, and 

 clarify them in xylol. The preparation should then be examined 

 with low magnifying power, because the bacilli appear in the tissue 

 (especially of the internal organs) in a very peculiar arrangement. 

 They are not singly or diffusely spread over wide areas, but always 



