300 PROCEEDINGS OF SECTION D. 



(c) Another layer much broader than (6) showing a recticu- 

 late or areolar appearance. 



{d) A sharply contoured narrow band resembling a base- 

 ment membrane. 



2. Cutis. Showing an undifferentiated mass of protoplasm of 



considerable thickness, with scattered nuclei. 



3. Muscular laver. More or less differentiated. 



At the injured spot we found that the following alterations 

 have taken place in the cuticle and in the cutis. In the centre of 

 the ulcer all the layers which we have mentioned as belonging to 

 the cuticle and epidermis are deficient. Passing towards the edge, 

 the basement membrane-like layer is first met wath, and then the 

 other layers in regular order, all presenting a more or less irregular 

 jagged appearance. There is no evidence of repair on the part of 

 any of these layers. From the cutis, however, a very decided 

 reaction has taken place, consisting in the separation of a definite 

 part of the cutis which is shut off from the rest of the cutis by a 

 well-defined line, although structurally it does not differ in appear- 

 ance from the cutis proper, excepting that nuclei were not detected 

 in it. This area in the centre of the ulcer forms a deep layer which 

 extends laterally on each side, thinning out rapidly from within 

 outwards so that it forms a kind of lens-shaped area occupying in 

 the depths of the tissue an area about equal in extent to the size of 

 the ulcer on the surface. Our interpretation of these appearances 

 is as follows : — 



At the site of the ulcer an injury had been inflicted upon the 

 worm, and had extended down as far as the cutis. The loss of 

 tissue affected chiefly the cuticle in the form of a crateriform 

 depression. There has been no reaction on the part of the cuticle 

 to repair the damage thus done. As regards the outer layers of the 

 cuticle this is what might have been expected, as living cells could 

 not be expected to be present in them to repair the damage. 

 In the deepest layers of the epidermis, however, where living cells 

 would be present at least in young individuals, some repair might 

 have been expected. In the outermost layers of the cutis, however, 

 there has been a very definite multiplication of the tissue, due 

 presumably to the activity of the cells scattered throughout it. 

 This activity has resulted in the production of a button-like area 

 which has been separated off from the rest of the cutis, and tends as 

 it were to plug the defect in the cuticle above and thus compensate 

 for the weakening in the wall of the worm. 



Text Figure I. 

 Section through an " ulcer." 

 c, Cutis with scattered nuclei ; cu. 1, cu, 2, cu. 3, cu. 4, various 

 ^ayers of the cuticle ; m., musculature of the body wall ; r.i., 

 ' repair tissue " below the point of injury. 



