eggs. Plant material is especially likely to be mistaken for parasites 
owing to its greater content of indigestible substances as compared 
with animal material. Aside from bones, which are usually readily 
recognizable, there is comparatively little in the way of animal material 
which passes the digestive tract undigested, but the high content of 
cellulose and related substances in plants furnishes an abundance of 
Fig. 71. Pollen-spore of a pine, Pinus insignis. Enlarged. From Campbell, 1902. 
undigested materials which may simulate parasites, and numerous 
seeds and spores simulate parasite eggs. 
Among the objects commonly present in feces and frequently 
mistaken for parasites are plant hairs. These are usually mistaken for 
nematodes of some sort, the hair being somewhat pointed at its free 
end and sometimes having a structure slightly suggestive of a 
strongyle bursa at the end originally attached. The writer has known 
these hairs to be mistaken for nematodes by a man of several years 
Fig., 72. Cell of yeast fungus, Saccharomyces cerevisiae, containing 4 spores. 
Enlarged. From Campbell, 1902, after Reess. 
experience in the field of parasitology and has called attention to one 
case in which such a plant hair was reported as a trichina larva in 
the blood. The homogeneous structure of these hairs and the lack 
of any internal structures resembling those in nematodes should be 
sufficient to distinguish them from worms. Fibrous connective tissue 
may sometimes be mistaken for nematodes, but here also the lack of 
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