44 Structure and Classification of Micro-organisms 



Aspergillus subfuscus is also pathogenic and highly virulent. 



Aspergillus niger. — Pathogenic and found at times in inflammation 

 of the external auditory meatus. 



5. Penicillium. — These are common green molds, widely dis- 

 seminated throughout the atmosphere and frequent sources of 

 contamination of the culture-media in the laboratory. Moist bread 

 exposed to the atmosphere soon becomes covered with them. They 

 are included in the group oi fungi imperfecii, and are characterized by 

 a luxuriant tangled septate mycelium, with aerial fruit hyphae, 

 ending in conidiophores, each of which divides into two or three 

 sterigmata, the tip of which forms a chain of rounded spores. The 

 whole germinal organ thus comes to resemble a whisk-broom or, as 



Fig. 14. — Penicillium. (Eyre.) 



Hiss describes it, a skeleton hand, in which the conidiophore cor- 

 responds to the wrist; the sterigmata, to the metacarpal bones; the 

 chains of spores, to the phalanges. 



None of the penicillia is known to be pathogenic either for man or 

 animals. 



Penicillium crustaceum (glaucum) is the most common source of 

 contamination of the laboratory media. 



Penicillium minimum, which may be identical with the preceding, 

 was once found in the human ear by Sievenmann. 



THE PROTOZOA 



The protozoa are unicellular animal organisms as differentiated 

 from the metazoa which are multicellular animal organisms. The 

 restriction, implied by the term unicellular is, however, too narrow, 

 for there are colonial protozoa that consist of many cells, yet share 

 other protozoan characters. 



For the purposes of this work, however, all protozoa are to be re- 

 garded as unicellular and the individuals independent of one another. 



Classification. — Many schemes have been devised for systematic- 

 ally arranging the protozoa, that which follows being an abbrevia- 

 tion of the standard classification, made to correspond with the 

 requirements of this work that deals only with the pathogenic forms. 



