THE LIVING ORGANISM 211 



such as acne, and feruncle (or boils), more 

 especially when cultures have been carefully 

 made from the strain of organism in the 

 patient's own body which is actually causing 

 the disease. This has now become a standard 

 treatment in such diseases. 



In diagnosis also these chemical reactions 

 have yielded great aid to practical medicine, 

 and to us here these diagnostic reactions are 

 of high interest because of the beautiful 

 examples they provide of the delicate struc- 

 tures and reactions which have become 

 evolved as a result of the increasing com- 

 plexity of design in living organisms. One 

 example must suffice as a sample of the 

 whole. A certain percentage of cases of 

 enteric fever are very difficult to diagnose 

 on account of absence or variation of import- 

 ant clinical symptoms characteristic of typical 

 cases ; but a very simple bio-chemical test 

 here furnishes a valuable indication. Enteric 

 fever is caused by a motile microscopic bacillus 

 (the Bacillus typhosus), which moves about 

 by means of long, fine, whip-like processes at 

 one end of a short stout, rod-like body. This 

 organism can readily be cultivated artificially 

 in nutrient broth and other artificial media, 

 and when a drop of this nutrient fluid, diluted 

 with a dilute solution of salt of the proper 



