90 



a slight invasion with eosinophils. Immediately under the 

 cutis vera the eosinophilic infiltration is seen to be very- 

 marked. The eosinophil es may be so numerous as to fill all 

 the lymph spaces, leaving only a more or less fine connective 

 tissue stroma supporting them. There is an increase in the 

 small blood vessels with well-defined walls. There is hyper- 

 plasia of the fixed connective tissue cells. Roughly circular 

 areas, consisting of embryonic connective tissue cells with 

 some mononuclear leucocytes, but with few or no eosinophils, 

 are seen. 



The caseous areas vary slightly in size; they have well- 

 defined margins and take acid stains intensely. Tissue 

 reaction round these areas appears to depend on their age. 

 There is a proliferation of the fixed cells and commonly a 

 marked epitheloid cell reaction with the formation of multi- 

 nucleated cells. Sometimes there is a well-defined fibrous 

 capsule. The nuclei of the cells within the areas show some 

 pyknosis, and the chromatim remains for some considerable 

 time. The protoplasm of the cells is apparently fused. 

 All tissues are included in this necrosis, and the in- 

 distinct forms of blood vessels and connective tissue strands 

 can be detected. In some of the areas a calcerous deposit 

 may be seen. More or less in the centre of the necrotic areas 

 are seen either circular or ovoid spaces containing debris and 

 a few leucocytes. These represent the spaces at one time 

 occupied by, and the remains of, a larval Nematode, and may 

 appropriately be termed "worm canals." Larvae or debris 

 are not found in all sections. This may be due either to the 

 fact that the section does not necessarily cut that portion of 

 the necrotic foci containing the larvae or to the complete 

 disintegration of larvae or debris. 



In some of the earlier lesions the larva is often to be seen 

 distinctly. It is easy to demonstrate the clear, homogenous, 

 finely-ridged cuticle, the musculature lying beneath, and the 

 primitive alimentary canal. The section may be transverse, 

 oblique, or longitudinal, and there may be more than one 

 section of the larvae in a necrotic area. In one area seven 

 transverse or oblique sections were seen. These probably 

 represent' as many individual larvae. For the most part, 

 however, only one worm is seen in each necrotic area, and 

 it is always more or less twisted and curved. 



In other parts of the section the worm is found sur- 

 rounded by only a small necrotic area. Often oblique and 

 transverse sections of the worm are seen extending in a more 

 or less regular line across the field of the microscope, repre- 

 senting the twisting and curving of one organism. 



