560 DISEASE IN WILD MAMMALS AND BIRDS 
The mode of operation of these hyphomycetes has 
usually been assumed to be a mechanical one, local 
colonization replacing healthy tissue or spreading along 
surfaces so that function is physically impossible. A 
support of this idea is to be found in the fact that inflam- 
mation, as produced by schizomyces, is trifling or absent ; 
the necrosis that occurs is due to choking off of tissue by 
the intricately tangled masses of mycelia and blocking 
off of air or blood supply. The existence of an infiltrating 
and necrotizing form in some parrots and gallinaceous 
birds, suggested to me that a toxin might be responsible 
for some part of mould action. Proof for this speculation 
was sought by injecting into the pectoral muscles of 
pigeons an emulsion of a dead mould and a filtered 
broth culture. Necroses occurred but only to an extent 
which I interpreted as due to the physical destruction of 
muscle by the injected material ; they were larger with the 
dead mould than with broth filtrate. I concluded there- 
fore that aspergillus perhaps has no toxin as usually 
described for bacteria. 
Types of Mycosis. 
Avian mycosis occurs in three different forms, two of 
which are probably of similar nature and two are fre- 
quently combined. The first variety, most often seen in 
gallinaceous and anserine birds, consists of thickening 
and opacity of the air sac walls, upon the surface of which 
either a curd-like pseudocoagulum or a velvety or fluffy 
mould growth appears. This variety usually begins 
about the anteroinferior pulmonary stoma on the right 
side extending thence to the related sac, upward toward 
the wing and downward to the abdominal spaces. 
Occasionally the middle thoracocervical space is involved, 
probably via the opening in the syrinx. Extension takes 
place by the way of normal passages, but when the growth 
is dense it also seems to occur by continuity through tis- 
sue. This variety may or may not be associated with the 
