CH. VIII.] BACTERIAL DECOMPOSITION. 225 



The amines are of considerable importance. Even 

 the relatively simple compounds mentioned above are very 

 active physiologically, causing contraction of non-striped 

 muscle, which generally results in a rise of blood pressure. 

 Histamine is a very powerful drug, and causes contraction 

 of the uterus. These bases are present in ergot, and are 

 produced by the action of micro-organisms on the proteins 

 of the infected rye. The physiological activity of ergot is 

 mainly due to the presence of tyramine and histamine. 



In addition to the putrefaction bases mentioned above, 

 many others have been identified. These bases are some- 

 times known as " ptomaines." 



Putrescine, NH 2 .CH 2 .CH 2 .CH 2 .CH 2 .NH 2 , is derived from 

 ornithine by the loss of CO 2 . Ornithine itself is NH 2 .CH 2 . 

 CH 2 .CH 2 .CH(NH 2 ).COOH, and is obtained by the hydro- 

 lysis of arginine (see p. 69). 



Cadaverine, NH 2 .CH 2 .CH 2 .CH 2 .CH 2 .CH 2 .NH 2 , is simi- 

 larly formed by the decarboxylation of lysine. 



A complete account of these compounds is given in 

 Barger's " The Simpler Natural Bases." 



Of the other substances mentioned, urocanic acid was 

 originally isolated from the urine of a dog ; hence its name. 

 Raistrick has recently obtained it from histidine by bacterial 

 decomposition. 



Phenol and p-cresol are mentioned again on p. 282. 



Indol and scatol are mainly responsible for the charac- 

 teristic faecal odour. They are important to the practical 

 bacteriologist, owing to the fact that only certain organisms 

 are able to produce them from tryptophane. For this 

 reason certain suspected organisms are grown in a suitable 

 medium, which is tested for indol after a given time. The 

 information thus obtained is used in arriving at a diagnosis 

 of the organism. The usual medium used is a solution 

 of Witte's peptone, and the incubation period is 2 to 8 days. 



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