ORGANISMS WHICH PRODUCE DISEASE 73 



Typhoid fever, which is commonest in early autumn, is 

 specially a disease of man, and not, under natural conditions, 

 of the lower animals. The disease is really a general infection 

 of the body. The organism is present in the circulating blood 

 early in the disease, and it tends specially to settle down and 

 damage the lymphoid tissues of the body, e.g. especially that 

 in the small intestine, the mesenteric glands, and spleen ; but 

 it is by no means confined to these, and may be found in practi- 

 cally any tissue or organ of the body. In carrier-cases it often 

 persists for long periods in the gall-bladder, and it may be ex- 

 creted not only in the faeces but also in the urine. Ulceration 

 of the small intestine is one of the most serious results of its 

 action ; and if one of these ulcers perforates through the wall 

 of the bowel, a fatal peritonitis may be set up. Haemorrhage 

 from the ulcerated bowel is another very serious complication, 

 and in some cases lung trouble, abscesses, etc., may occur. 



Preventive, and also therapeutic vaccine-treatment is now 

 extensively used, and very favourable results have been re- 

 ported in our own and in foreign armies. 



B. dysenteriae, of which there are numerous closely-allied 

 varieties, is the cause of one form of Dysentery usually 

 spoken of as Bacillary, as contrasted with Amoebic, Dysentery 

 (see p. 84). 



Numerous saprophytic and putrefactive organisms may 

 microscopically resemble members of the Coli-Typhoid group. 

 Most of these, however, e.g., the Proteus group, which are 

 common in the intestine, liquefy gelatin, and show other differ- 

 ences on culture. B. pyocyaneus is a member of a colour-pro- 

 ducing group of organisms, and forms a greenish or bluish-green 

 pigment (p. 38), which gives a characteristic coloration to its 

 cultures, and sometimes also to the pus which it may produce 

 in suppurative infections. B. proteus, B. pyocyaneus, and similar 

 organisms, though commoner as saprophytes, are frequently 

 found in chronic ear disease, and sometimes in urinary and 

 other infections. 



Anaerobic Group of Pathogenic Bacilli. The pathogenic 

 anaerobes have the common characteristic that they will grow 

 only in the more or less complete absence of oxygen. Some of 

 them are closely allied in other ways : whilst others, for example 

 certain influenza-like organisms, and the B. fusiformis (the 

 latter possibly not really a bacillus at all), otherwise differ 

 radically from the group as represented, say, by B. tetani or 

 B. oedematis, which are its most characteristic members. 



Bacillus tetani, the organism which causes Tetanus or Lock- 

 jaw, a disease which attacks the horse as well as man, and is 



