CHAPTER VII.—PHENOMENA OF VEGETATION.—PARASITES. 36 9 
Excrescences of the kind just described and local hypertrophies caused by Fungi 
have been fitly compared with galls and have sometimes received that name. 
It is obvious that all these mycetogenous deformationsand new formations and the 
phenomena also of simple destruction are in direct causal connection with the process 
of feeding the Fungus. In the latter case we see directly that the Fungus grows at 
the expense of the parts which are destroyed, the substance of its own body constantly 
increasing. In the case of tumours and hypertrophies there is often at first a striking 
over-production of building material, as starch, and this is afterwards used for the com- 
pletion of the development of the Fungus. In connection with this it often happens 
that the parts deformed by the Fungus are also killed prematurely; they die and are 
decomposed sooner than the same parts when free from the Fungus and not deformed. 
But every conceivable gradation is found in this respect in different species and some- 
times in different individuals between the parasitism which quickly destroys its victim 
and that in which parasite and host mutually and permanently further and support 
one another,—the relation which is most conspicuous in the formation of Lichens 
and which Van Beneden ! has termed mufualism. 
The phenomena here touched upon have not been submitted in any case to a strict 
physiological analysis; but the general nature of the enquiry is so obvious that it is 
unnecessary to discuss it here. 
In the following summary of the chief phenomena and combinations which 
actually occur we must keep the Fungi which live on animals distinct from those 
which inhabit plants. 
FuncI WHICH ARE Parasitic on ANIMALS. 
Section CIV. The Fungi which attack the bodies of living animals furnish 
a series of instructive examples of the phenomenon of facultative parasitism (see 
page 356). 
A number of species of Eurotium and Aspergillus (Sterigmatocystis), which all 
occur chiefly as saprophytes and in that mode of life reach their full development, in 
some cases even forming sporocarps, are able to migrate to the bodies of warm- 
blooded animals and live at their expense, producing an abundance of typical gonidia, 
but not, as far as we know, arriving at the formation of sporocarps. Their vegetation 
causes or promotes a diseased state of the parts, known to physicians as mycoszs. 
Aspergillus flavus, A. niger and A. fumigatus, Eurotium repens and Aspergillus 
glaucus are characteristic promoters of the disease of the human ear which bears the 
name of ofomycosis aspergillina”. The Fungi find a nidus in the diseased (serous) or 
excessive normal secretions of the skin, and their rapid growth causes inflammation 
and excoriation of the parts. But in these cases, as Siebenmann urges, they do not 
penetrate through the epidermis and are not developed in the healthy ear, so that they 
virtually retain their saprophytic character, however decidedly they must be considered 
to be promoters of disease. 

-1 Animal Parasites and Messmates (Internat. Scientific Ser. xix). See also De Bary, Die 
Erscheinung d. Symbiose, Strasburg, 1879. 
2 Siebenmann, Die Fadenpilze Aspergillus, &c. u. ihre Beziehungen z. d. Otomycosis aspergillina, 
Wiesbaden, 1883 ; many special treatises on the subject are enumerated in this publication, 
[4] Bb 
