324 THE MICROSCOPIST. 



investigations. Adulteration of flour with alum, etc., 

 may be detected by dissolving the. alum and recrystalliz- 

 ing under the microscope. 



Coffee 'is adulterated with chiccory, wheat, corn, etc.; 

 tea with foreign leaves, Prussian blue, clay, etc.; choco- 

 late with brickdust, peroxide of iron, animal fat, etc. 



IY. PARASITES. 



Parasites are animal or vegetable organisms which live 

 temporarily or permanently upon or within another or- 

 ganism for their nourishment and development. Casual 

 visitors for the sake of moisture, warmth, or products of 

 decomposition (as many fungi and infusoria) are called 

 pseudo-parasites. Van Beneden distinguishes between 

 messmates which are nourished in common, mutualists 

 which live on and serve each other, and parasites which 

 live at others' expense. 



In this department of science the student will do well 

 to consult Cobbold's magnificent work on Entozoa, and 

 two of the recently published international scientific series 

 of books, viz., Fungi, by Cooke and Berkely, and Animal 

 Messmates and Parasites, by Van Beneden. 



The plan of Wagner, in his Manual of General Pathol- 

 ogy, is followed in the present outline, so far as classifica- 

 tion is concerned. 



I. VEGETABLE PARASITES OR EPIPHYTES. 

 I. FUNGI. 



The general character and development of fungi have 

 been described at page 136. The subject of polymor- 

 phism also has been referred to as indicating the uncer- 

 tainty of distinguishing genera and species. Cooke re- 

 minds us, however, that polymorphism can only be based 

 upon actual organic continuity, the observance of which 

 in such minute organisms is necessarily difficult. 



