194 The Microscope. 



" cells " could be seen. They begin to appear, such was the claim, 

 after the specimen has been left at rest for some time, and exhibit 

 form-changes just as active as are those of the amoeboid " cells " 

 of the frog's blood. They migrate under the very eye of the 

 observer in curved, sometimes straight routes, traversing the field 

 of vision in about one hour. The number of migrating " cells " 

 is considerably increased, if the cornea can be brought to inflam- 

 mation by cauterization with nitrate of silver. Since 1864 the 

 " cornea cells " in consequence of their discoveries, were divided 

 into the " fixed " and the " wandering " ones, the former being 

 embedded in the basis substance, the latter migrating in certain 

 insterstices in varying numbers. Cohnheim, in 1867, announced 

 the idea that all inflammatory or pus corpuscles have migrated 

 into the tissue of the cornea from without, being nothing but 

 colorless blood-corpuscles that have left in an active locomotion 

 the cavities of the capillary blood-vessels. Such vessels, as is 

 well known, exist only at the border of the cornea, whereas the 

 substance of normal corneae is entirely destitute of vessels of any 

 description. It was especially the frog's cornea which served as a 

 battle-field for the adherents of Cohnheim on the one hand and 

 the opponents (F. A. Hoff"raan, S. Strieker and others), who 

 proved that in inflammation the formerly " fixed cells," after hav- 

 ing split up into a number of pieces become " wandering cells." 

 At the beginning of the eighth decade there were three parties en- 

 gaged in the fight regarding the origin of the " migrating cells," 

 those who claimed that the sole source of such cells is the blood 

 and blood-vessels ; those who maintained their origin from fixed 

 cornea cells exclusivel}^ ; and those who admitted both ways. 



The cornea is an extremely tough and elastic tissue, equal in 

 its consistency to cartilage, as everyone knows who has tried to 

 cut through it ; that in inflammation the basis substance becomes 

 softened, and admits of a locomotion of " migratory cells," soft 

 protoplasmic bodies themselves, was intelligble. But how could 

 we explain such locomotions in a normal cornea, or through the 

 peripheral portions of the cornea, when the inflammatory focus, 

 artificially produced, was in its centre ? 



For those who claimed that the cornea is traversed by lymph- 

 channels, lined by endothelia, and holding, here and there, in a 

 rather loose way, fixed cornea-corpuscles, the explanation of 

 the locomotion of " migrating cells " could not be diflficult. To 



