﻿184 Pi'oceeclings of the Royal Pkydcal Society. 



There is, however, too little data to admit of any certainty 

 upon these points. The method of growing out, and the 

 apparent capacity for movement of these large creatures, 

 seem to indicate that they serve to distribute the parasite 

 over a wider area of the host tissue. Fig. 12 is a drawing 

 of a section through part of one of these individuals. 

 The parasite here is very large and irregular in shape. At 

 one point (P) what appears to be a stage in the process 

 of plasmotomy may be seen. Empty portions of the 

 envelope are seen, secreted by parts of the parasite during 

 its passage through the connective-tissue nodule. The 

 parasite here was very large, and stretched through quite 

 a number of sections. It is drawn under a lower power 

 than the other figures, i.e., three-fourths of their size. 



The parasite as found in the intestine shows all the 

 characters described above. It lies in the thin layer of 

 connective tissue that runs up the villi and between the 

 muscular sheath of the intestine and the epithelium lining it. 

 Icthyosporidium is essentially a tissue parasite, and causes 

 great nodules to be formed in the spaces between the epi- 

 thelium of the villi, giving the intestine a most remarkable 

 appearance when seen in section. The whole wall of the 

 intestine may grow out to form a csecum of some size, 'O to 

 1 cm. in length. The nodules of connective tissue, both 

 here and in the liver, are at first very definite, with well- 

 marked concentric layers of cells. Later, as the parasites 

 increase in number, the nodule enlarges very much, and the 

 cells composing it show a tendency to become separated 

 from each other, and may show hypertrophy of the nuclei. 

 There appears to be a tendency for each parasite within 

 the nodule to act as the focus of a nest of connective- 

 tissue cells. This of course separates the parasites from 

 one another, and greatly increases the extent of the area 

 of reacting host tissue. In late stages this tendency becomes 

 less marked in the centre of the nodule, which becomes 

 rather broken up, but seems always to occur at the edges 

 of the invading mass of connective tissue. I have never 

 seen the Idhyosporidium here described in the epithelium 

 of the intestine, but the growing nodules seem occasionally 



