494 



Mr. G. F. Dowdeswell on the Changes of [Jan. 18, 



process should be of longer duration) by a seton o£ silk thread. The 

 animal having been killed at the proper period, and its cornea excised 

 and immersed in half per cent, solution of gold chloride for 60 minutes, 

 and exposed in a light warm place, when sufficiently coloured a small 

 portion of the inflamed part is placed in a solution of potash till the 

 ground- substance is completely dissolved. Care is requisite to hit off 

 the exact point for this, a few minutes too much or too little rendering 

 the preparation useless. If the time of exposure is too short, obviously 

 the ground-substance is not wholly dissolved, and nothing is seen ; if it 

 is too long, the potash begins to act upon the protoplasm, and the cor- 

 puscles cannot be separated nor distinguished. It was found that, if the 

 cornea was put into a 20 per cent, solution of pure potash cold, and 

 then subjected to a temperature of 40° C, 50 minutes was the proper 

 time required for the action of the potash. 



"When sufficiently acted upon, the cornea is transferred to slightly 

 acidulated water, to stop any further action of the potash, then placed on 

 a slide, if necessary teased out lightly, and preserved in glycerine. 



In a preparation made by the above methods a number of migratory 

 cells will be apparent under the microscope, some of which are entangled 

 amongst the processes of the fixed corpuscles. All these are in a state of 

 active cell-division and assuming diversified forms, but are very readily 

 distinguished from the fixed corpuscles by their being devoid of processes, 

 of somewhat darker colour, and by their presenting a more opaque and 

 solid appearance*. The fixed corpuscles, with their processes, show no 

 alteration whatever. As may be seen from the figures (Plate 10. group IL), 

 the processes radiate from the bodies in a natural and symmetrical manner, 

 and the ramifications are as perfect as ever. This would certainly not be so 

 if segmentation had occurred ; for in that case one side at least of each 

 newly divided corpuscle would be devoid of processes. Nothing ap- 

 proaching to such a condition is ever seen. In inflamed preparations, as 

 in normal ones, fixed corpuscles are occasionally met with containing two 

 nuclei or a double nucleus ; but this appearance is not often seen, and 

 not more frequently in later than in earlier stages. 



In conclusion it may be stated that in the whole number of successful 

 preparations of corneas which have been examined (amounting to upwards 

 of twenty), no single instance has occurred in which any distinct ap- 

 pearance of segmentation can be made out. The most careful scrutiny 

 of the preparations fails to detect any difference whatever, as regards 

 their forms or aspects, between the fixed corpuscles of inflamed corneas 

 and those of normal corneas prepared in a similar way; nor would 

 it be possible to distinguish preparations of the two classes from each 

 other, were it not for the presence of migratory cells in the inflamed 

 structure. 



In the drawings representations are given both of normal preparations 

 ^ Tbis IS not adequately shown in the drawings. 



