MUCORINE FUNGI 43 



aspergillus is the original cause of the diseased condition, or whether it 

 merely finds an entrance in places where the natural resistance of the tissues 

 is already lowered by injuries such as the attacks of other micro-organisms. 

 The spores are omnipresent, and accidental invasion is so easily possible 

 that every case must be judged on its own merits. 



There remain to be mentioned as possible pathogenic organisms a few 

 species of the genus Mncor, a mould-fungus of the order PJiycomycctcs. 

 They arc much less highly organized than the Aspergilli. The mycelium 

 consists of branched, ramified, non-septate hyphae, from which rise vertical 

 branches (aerial hyphae) that bear the spore capsules (sporangia). When 

 injected into the blood the spores of M. coryinbifer and of M. rJiizopodi- 

 fonnis set up lesions similar to those of aspergillus spores ; but only one 

 case of spontaneous infection has ever been observed in man. It is worthy 

 of remark that those species of Mucor and Aspergillus which are capable 

 of growing in the tissues of warm-blooded animals flourish only at high 

 temperatures (37 C.), whilst those which are satisfied with less warmth grow 

 in the tissues cither badly or not at all. 



