CONDITIONS OF LIFE OF THE LOWER FUNGI. 501 



of the fungi. These means are identical with the disin- 

 fecting agents which have recently hecome of so much 

 importance. 



Finally, the investigations as to the biology of the 

 lower fungi must not be limited to the individual; the 

 behaviour of a continued series of individuals must be 

 taken into consideration. More especially we must direct 

 our attention to the occurrence of modifications to the 

 formation of varieties, races, and species. 



The discussions in the following pages are limited 

 to those fungi, which are of importance from a hygienic 

 point of view (mould fungi, yeast fungi, and fission 

 fungi); with regard to the other fungi and micro- 

 organisms which were mentioned in studying the mor- 

 phological characters, we must refer to de Bary's 

 excellent description of the morphology and biology of 

 the fungi. 



I. CONDITIONS OF LIFE OF THE LOWER FUNGI. 



In order to understand the nutritive processes, it is in Conditions of 

 the first place necessary to take a short survey of the 

 chemical composition of the fungi. We must then ascer- 

 tain the importance of the individual nutrient materials, 

 in the first place of the nitrogen, and then of the carbon, 

 hydrogen, and combined oxygen, of the mineral sub- 

 stances, of the water, and, finally, of the free oxygen. 

 Special attention must also be paid to the concentration 

 and reaction of the nutrient mixture. Of less import- 

 ance is the influence of atmospheric pressure, light, 

 electricity, and mechanical movement; while the action 

 of various temperatures, the fermentative action, and the 

 concurrent growth with other fungi are of very great 

 importance in the development and growth of the indivi- 

 dual micro-organisms. 



In almost all these points the mould fungi, yeast 

 fungi, and fission fungi show such differences that each 

 must be separately studied. 



