101 



PART II. 



MORPHOLOGY AND CLASSIFICATION OF THE MICRO- 

 ORGANISMS. 



The micro-organisms which have as yet been The micro- 



., organisms 



recognised as exciting agents of fermentation and which interest 



putrefaction, or of disease, belong almost entirely ^ 

 to the lower fungi. Certain preliminary observations fungi. 

 render it probable that organisms which belong to other 

 classes of plants or animals, for example the algae, the 

 iiagellata, and the protozoa, may also occasionally act as 

 parasites, and become of hygienic interest ; but in the 

 meantime the known facts are too few for a systematic 

 review of this part of the subject, and it is therefore 

 sufficient to include here only those micro-organisms 

 which are of special importance for us, and which 

 belongto the lower fungi. 



In order to indicate the place of the lower fungi in the 

 system of the plants the following short sketch is given, 

 and the botanical handbooks, more especially the paper 

 by Frank on the Cryptogams in Leunis's Botany, and 

 de Bary's Comparative Morphology and Biology of 

 the Fungi, will furnish further details. 



The fungi, mycetes, belong to the cryptogams, that Place of the 

 great division of the vegetable kingdom which is vegetable 

 characterised by propagation by means of spores, in kin ? clom - 

 contrast to the other great division of the phanerogams. 

 The phanerogams bear flowers and produce seeds, in 

 which the various parts corresponding to the future 

 structures of the plants are already distinguishable ; 

 the cryptogams are flowerless, and propagate by means 

 of the spores just mentioned, that is to say, by small 

 cells, which show no differentiation and, when present in 

 large numbers, resemble one another. The cryptogams 



