INFLAMMATION. 141 



the foreign bodies or substances that are experimentally in- 

 troduced into tlie bodies of vermes. This reaction is analoyuus 

 to the reaction of the mammalian leucocytes. 



The discussion so far, has been with reference to animals 

 that possess no blood or vascular systems, or at least only in 

 a rudimentary ft.)rm. 



\'ertebrates are more highly organized and are consequently 

 more responsive to stimuli than invertebrates. Mammalia arc 

 the most complex in structure of all animals and they are like- 

 wise most responsive to stimuli. 



The mammalian cornea is a nonvascular structure being 

 composed of fused layers of fibres arranged parallel to the sur- 

 face. Between the layers of fibres connective tissue cells and 

 lymph spaces are foimd but no nerves. The cornea is covered 

 externalb,- bv the conjunctiva. If tlie cornea be irritated there 

 will l)e a reaction, the extent of which depends upon the in- 

 tensit}' of the irritant. A puncture of the cornea with a sterile 

 needle produces the following reaction or tissue changes ; (a) 

 within a few hours after the injury the affected area appears 

 swollen and the cells that were punctured begin to degenerate 

 while the uninjured cells immediately surrounding the needle 

 puncture become tumefied and vacuolated; (b) from twenty to 

 thirtv hours after the puncture, wandering cells appear in and 

 around the injured area, and as the cc)rnea is nonvascular they 

 must be migratory connective tissue cells; (c) by the third 

 or fourth day the punctured cells will have been removed, by 

 solution or otherwise, from the affected areas. Those cells sur- 

 rounding the injure- will ha\-e divided liy mitosis, the newly 

 formed cells replacing those that were destroyed and the 

 wandering cells will have migrated from the injured focu.^. 

 (The destroved epithelial cells of the conjunctiva are replaced 

 by those next to the injury). 



If sterile iron dust, or other insoluble granular material i^ 

 aseptically introduced into the cornea, a reaction, as described 

 above, will take place, and, in addition, the migratory connec- 

 tive tissue cells Vv'ill ingest or incorporate the introduced par- 

 ticles and carrv them out of the injured focus. 



When the cornea is injured more severely, as by the ap- 

 plication of a caustic solution (irritant), in addition to the 

 above reaction, a migration of leucocytes from the marginal 

 corneal vessels usually occurs within thirty hours. Some of 

 the invading leucocytes become destroyed and some of them 

 may multipfv, but they usually all disappear from the point of 

 mjurv within from forty to fifty hours. The length of time 



