

THE MIGRATING OR VAGRANT CELLS OF THE CORNEA. 377 



owing to their increased lustre, after being macerated in the 

 fluid for a few minutes. 



Their rapid alterations of form are exactly similar to those of 

 the amoeboid cells of the blood of the Frog, or the free pus cor- 

 puscles found in the aqueous humour of that animal. They are 

 of a remarkably elongated and attenuated shape in the tissue of 

 the cornea. They move from place to place ; a phenomenon 

 that is only intelligible when, in addition to the mobility of 

 the cells, the permeability of the medium (the corneal tissue) 

 in which they are observed, is clearly recognized. Referring 

 the latter for subsequent consideration, we shall here accept the 

 permeability of the tissue as a fact, and follow the cells alone. 



Migrating cells are found at all depths of the corneal tissue. 

 The course they pursue varies, and is usually very devious,* 

 though sometimes rectilinear. In the latter case the passage 

 of a cell across the field of a Kellner's microscope occupies 

 from half an hour to a whole hour (v. Recklinghausen). 



Migrating cells may be seen in the fresh cornea of other ani- 

 mals besides the Frog. Amongst Mammals, observations have 

 been made in respect to them by v. Recklinghausen on the 

 Rat, Rabbit, Dog, Ram, Ox, and Pig ; but it is requisite in the 

 case of the thicker cornese to make sections parallel to the 

 surface with a sharp knife. The movements of locomotion are 

 not in all cases, but sometimes just as evident as in the Frog. 



The migrating cells of the cornea of the Frog change into 

 highly refracting roundish bodies provided with only short 

 processes or projections, when placed in a moderately strong 

 solution of sugar (v. Recklinghausen, Engelmann). The number 

 of migrating cells undergoes considerable increase, if inflamma- 

 tion be produced in the cornea by producing an ulcer with nitrate 

 of silver (purulent infiltration). The same occurs also if in- 

 flammation be excited by any other cause (traumatic keratitis.) 



As soon as the amoaboid characters of the pus corpuscles found in 

 the aqueous humour after ulceration of the cornea had been observed, 

 proving the accuracy of the view previously maintained by Virchow, 

 that pus corpuscles are identical with white blood corpuscles, it was also 

 observed that the pus corpuscles found in parts of the cornea infiltrated 



* v. Recklinghausen, loc. cit., pp. 157 371. 



