KOCH'S TUBERCULIN MOULDS 



brane, dry above, and often thrown into folds, which in 

 two or three weeks more becomes moistened by the fluid, 

 and finally breaks up into ragged pieces and sinks to the 



- Columella 



Acicular crystals of 

 calcium oxalate 

 Sporangium 



Hyphe 



Mycelium 



FIG. 2. MUCOR MUCEDO. (After Baumgarten.) 



bottom. The cultures (which thus require from six to 

 eight weeks for their growth), when fully ripe, are evapo- 

 rated to a tenth of their bulk in a water-bath, and filtered 

 through earthenware or infusorial earth. 



Sterigmata with 



spores 

 Fructification 



X 



Hyplie 



Mycelium 



FIG. 3. ASPKRGILLUS G-LAUCUS. 



Moulds. These are for the most part saprophytes, 

 though pathogenic varieties are also to be found among 

 them. They form spores which, like those of bacteria, are 

 marked by the strong resistance they offer to external 

 influences, and which develop under favourable circum- 

 stances into complete individuals. They sometimes con- 

 tain shining drops like fat-globules. 



