734 " William Patten 



acid, and, after beiiig- fixed, were washed in 35, and 70^ alcohol. The 

 sliells are then opeued and the edges of the mantle dissected oiit with 

 ncedles. In thìs manner, the shape of the mantle is retained, whereas 

 if removed before hardening it becomes very much coiled and twisted 

 by the reagent. If now one tries to cut the curved mantle edge, itwill 

 be a mere chance if accurate cross sections are obtaìned. Moreover, 

 one is never sure of getting sections of eyes in the desired stages. To 

 save timo, I cut each mantle edge, according to its size and curvature, 

 iuto three or four pìeees, which are then tolerably straight. As man}^ 

 as 20 or 30 of these pieces, after being stained etc., are transferred 

 to a wateh-glass full of melted paraffine. With a little care , 10 or 12 

 pieces, with their long axes parallel, may be arranged in a bündle on 

 the bottom of the watch-glass. After cooling, the bündle may be cut 

 out and sectioned »in toto(f. 



Weak Solutions of sulphuric acid in sea water (15 drops to 30 grams) 

 have beeu used with good results ; the only drawback to this reagent 

 is the difficulty of getting a sharp stain. Kleinenberg's alcoholic 

 haematoxylin seems to give the best results. There are difficulties in 

 using sulphuric acid : for it is neeessary to fix the mantle while stili 

 attached to the shell, so that crystals, seriously interfering with the 

 sectioning, are precipitated upon the tissues. Some of the sections were 

 examined in balsam, others in glycerine or acetate of potash. A large 

 number of sections both of young and adult eyes were mounted in 

 Sandarack dissolved in absolute alcohol. For fibrous structures and 

 very fine nerves , it gave good results on account of its low index of 

 refraction, but at the end of two or three w^eeks the sections were abso- 

 lutely worthless. 



In order to study the very complex structure of the adult eye, it 

 was fouud neeessary to resort to a dififerent reagent for almost every 

 component of the eye. A great deal of time was spent in trying to 

 discover some method by which good sections could be obtained, show- 

 ing, at the same time, ali the various structures. 



One of the most useful reagents was chromic acid ' ; the raost 

 varied results were obtained by different methods of application as 

 regards strength , time of action, and temperature of the solution, or by 

 various combinations of ali three. For instance chromic acid of 7.20 to 

 Vò Vo ) for 30 to 40 hours , utterly failed to give any conception of the 



1 Ali Solutions of chromic acid were made frora a 1% solution in distilled 

 water, subsequently diluted with sea water. 



