876 SUMMARY OF CURRENT RESEARCHES RELATING TO 



The best sections of the retina were prepared by fixing and 

 hardening in the watery solution of osmic and chromic acid (1/4 per 

 cent, chromic acid, 1/10 per cent, osmic acid) in which they were 

 placed for from 24-48 hours, and then put into alcohol and carbolic 

 acid for 14 days more; the retina was then stained in bulk, Kleinen- 

 bcrg's solution being the best when thin sections are required ; 

 and finally, infiltrated and imbedded in cacao butter ; this gives the 

 thinnest and best sections with a minimum amount of trouble. A 

 piece of the eye must be dehydrated in alcohol, cleared in oil of 

 cloves, and placed in the butter melted at 35° C. for from four to six 

 or even twelve hours ; it should then be imbedded in the butter in the 

 usual way. When the butter is quite hard the sclerotic and part of 

 the choroid should be detached with a sharp scalpel, so that the retina 

 and part of the choroid alone remain to be cut into sections. The 

 mass cut away should be replaced by a little melted butter. 



Substitute for Bone-grinding.* — Prof. W. Flemming uses bones 

 which have become perfectly decalcified by the prolonged action of 

 chromic acid, hydrochloric acid, and spirit. From this material 

 sections 10 to 25 p thick are made under spirit, and then steeped in 

 water. After having been dried on blotting-paper, they are spread 

 out on a glass plate, and then covered with another. The glass 

 plates with inclosed sections having been placed in a dish are covered 

 up with spirit. In about half an hour the sections have become 

 sufficiently flat to allow of their removal to absolute alcohol. When 

 thoroughly dehydrated, they are spread out flat on a glass plate and 

 covered with a layer of blotting-paper, over which is laid another 

 glass plate. In this position they lie for at least a day, until they are 

 dry. The drying may be hastened by slight heat. 



In order to mount the sections warm balsam must be employed. 

 A drop of melted balsam is placed both on the slide and cover-glass, 

 the section is spread out carefully in the balsam on the slide, and the 

 cover-glass then imposed. A stiff clip must be put on at once. 



The defect of this method is the large areas of tissue which 

 sometimes fail to show the canals and canaliculi ; a defect caused 

 probably by their walls having become agglutinated during decalci- 

 fication and having failed to separate when drying. But with this 

 exception, the process may be recommended as an efficient substitute 

 for the slow and tedious process of grinding bones down for micro- 

 scopical preparations, the canals and canaliculi in the dried and 

 decalcified sections giving as good results as those obtained by the 

 more tedious and difficult method. 



Preparing Mid-gut Gland (Liver) of Mollusca.j — Dr. J. Fren- 

 zel's examination of the gland tissue was made in dilute sea-water or 

 in salt solution of not less than one per cent. Hardening, especially 

 of sea molluscs, did not succeed perfectly (sublimate in aq. dest., sea- 

 water, or weak spirit act best ; osmic acid is useless as it does not 



* Zeitschr. f. Wiss. Mikr., iii. (1886) pp. 47-9. 



t Arch. f. Mikr. Anat., xxv. (1885) pp. 48-S-i (1 pi.). Cf. Zeitschr. f. Wiss. 

 Mikr., iii. (1S8G) pp. 85-G. See this Journal, v. (1885) p. 792. 



