64 MORPHOLOGY 



or hemi-cellulose, like most plant cells, has been held for 

 years by a large number of bacteriologists. Recent research 

 has shown that the cell wall in the majority of species is 

 more like that of certain animal cells than of plants. The 

 cell wall is like chitin. It is insoluble and splits into 80 per 

 cent to 90 per cent of a nitrogenous carbohydrate glycosamin 

 (Wells). Chitin is an amino-compound of a carbohydrate. 

 It is a polymer of a simple animal carbohydrate as cellu- 

 lose is a polymer of a simple plant carbohydrate (Wells). 

 Chitin is found in quite a few places, such as on the wings 

 of certain insects, on the coverings of beetles, and in the shells 

 of certain crustaceans, such as the crab and lobster. 



No definite carbohydrates have been reported in the bac- 

 terial cell, and proven absolutely to be present. Certain sub- 

 stances similar to glycogen have been reported in Bacterium 

 tuberculosis (Levene). In some few bacteria, according to 

 Cramer, when treated with iodine, a substance giving the blue 

 color reaction for starch is noted. 



Chlorophyll has been reported in some bacteria. On inves- 

 tigation it has been found that it is not correct to class these 

 organisms as bacteria and that they should be placed among 

 the algae or Schizophyceae. Sulphur granules have been noted 

 in certain species of bacteria in the class Beggiatoaceae. 



Pigment granules are noted among some species of bacteria 

 (chromogenic) when certain definite conditions are provided. 

 The chromogenic bacteria and the chemistry of pigments will 

 be considered in a following chapter. 



