56 
broken down). ‘There is not the slightest possibility that 
an A cyst could ever become a B cyst, or vice versd. And 
now to describe the latter. 
Fig. 6 is part of a section through the periphery of 
the lower cyst in the appendage of fig. 4. All around 
(though the upper cyst happens to be close to it on one 
side) is the infiltration, a condition easier to describe ver- 
bally than to draw, as it would be most difficult to 
reproduce except very diagrammatically. 
These pseudocysts arise as the result of an endeavour 
on the part of the host to limit the infiltrated area by the 
arrangement of the hypertrophied connective-tissue in a 
series of concentric layers round the centre of infection. 
(The marked hypertrophy here is in strong contrast to 
its complete absence in the A cysts). This re-action of 
the host, not always so well-defined, seems to be without 
much success, for the parasitic invasion usually spreads 
further, often leading to another attempt at restriction ; 
in fig. 4 for example, the upper pseudocyst is of later 
formation than the lower. Young ones, therefore, are 
simply areas of diffuse infiltration with the layers con- 
centrically arranged; but, with age, and probably, to a 
certain extent, the pressure of the surrounding parts on 
the enclosed tissue, the cells of this latter disintegrate 
and degenerate, leaving a mass of spores embedded in their 
remains as a ground-substance, with frequently patches or 
islands free from spores and staining only with the plasma 
stain (deg.). The spores are in a much more closely 
packed condition than in the comparatively loose, infil- 
trated tissue of the appendage (not shewn in the fig.). It 
need hardly be added that there is no trace of endoplasm, 
nor of sporoblast-formation round the margin, nor, of 
course any ectorind, and, in fact, no sharply-marked ex- 
ternal limit 
a great contrast to fig. 5. The periphery 
