THE HYPHOMYCETES 169 



The spores cause the death of rabbits on intravenous 

 injection. Most cases of aspergillosis occur among bird 

 fanciers, especially those handling pigeons. In the birds 

 the disease takes a pulmonary form, and A. fumigatus 

 is most frequently found. 



Penicillium glaucum, the commonest mould, is seen as 

 a pale bluish-green fur on jam and damp surfaces. It 

 produces a peculiar musty odour. The mycelium consists 

 of horizontally arranged straight or slightly undulating 

 jointed filaments, from which the spore-bearing hyphae 

 stand vertically up, dividing at their upper ends into 

 forks (basidia), from which fine processes branch off 

 (sterigmata] in the shape of a hair pencil, and are segmented 

 at their ends into rows of fine globular spores or conidia. 

 The mould grows well on bread-pap in the form of a 

 fur, white at first, but afterwards green. On gelatin 

 plates fine threads diverging from a point, and not giving 

 rise to sharply defined colonies, radiate over a consider- 

 able surface. The spore-bearing hyphae which rise above 

 the level of the gelatin are put in motion by air currents, 

 when the spores disperse. The earliest formation of 

 spores takes place in the centre of the colonies, and is 

 indicated by a green colour. The gelatin is liquefied. 



The volatile arsenical compound, which is given off by 

 arsenical wall-papers to cause poisoning in the tenants of 

 the room, is almost certainly liberated from its combination 

 in the pigment by micro-organisms thriving in the paste. 

 Penicillium, Mucor, and Aspergillus are found to be 

 capable of so acting, most marked powers being given by 

 P. brevicaule. Gosio has elaborated a test whereby 

 P. brevicaule is used for the detection of minute amounts 

 of arsenic (see Glaister's ' Arsenic Gas Poisoning '). 



Brown mould is brownish-yellow in colour, and is dis- 

 tinguished from P. glaucum, which it otherwise resembles, 

 by its closely-felted mycelium, the hyphae being scanty, 

 ramified, and segmented. It grows on gelatin, which it 

 quickly liquefies. According to Trelease, this mould is 

 identical witli the Cladothrix dichotoma (</.?;.). 



Microscopical Examination of Moulds. Moulds cannot 

 be easily moistened with water, owing to the presence on 

 their surface of a very thin layer of fat. Alcohol to which 

 a little ammonia has been added removes Ihe fat, after 

 which they can be mounted in glycerin or glycerin and 



