614 EECOKD OF CURRENT RESEARCHES RELATING TO 



using, and are left tberciu from six to eighteen hours, according to 

 the rajiidity with which the elements take uj) the indigo. When 

 sufficiently stained the sections are placed in strong alcohol, and are 

 ready for mounting. 



The sulphindigotate of soda solution is prepared, according to the 

 process devised by Mr. Bullock, by first digesting best Bengal indigo 

 with Nordhausen sulphuric acid. The excess of acid is then removed 

 by washing, the colouring matter precipitated with chloride of 

 sodium, and left standing for several days. The precipitate is then 

 separated from the mother liquor by filtering through flannel, 

 and the excess of chloride of sodium washed out by pouring cold 

 water through the filter until the colouring matter begins to dissolve. 

 The washing is then stopped, and the precipitate dissolved in warm 

 distilled water to saturation, which makes a solution of a deep 

 greenish-blue colour. 



The efifect of this mode of staining is to leave the nuclei bright 

 red, while the formed material of the cell is slightly tinged with 

 blue. The connective tissue fibres become stained with a deep blue 

 colour, while the blood-vessels are purplish and mapped out with 

 surprising distinctness. Epithelium and hair take this staining in a 

 very curious manner, inasmuch as the cells of different ages take 

 different colours, ranging from a brilliant emerald-green to purple- 

 violet and olive-green, thus affording a valuable means of differentia- 

 tion, especially in epitheliomas, where the so-called j^earls are brought 

 out with great distinctness, being of a different colour from the rest of 

 the cells. 



This process seems somewhat troublesome, especially if the 

 microscopist attempts to make the indigo solution himself. But, even 

 if it should jirove so, the result obtained is well worth the pains 

 taken, and fully repays the outlay of time and patience bestowed 

 upon it. 



Isolation of the Optic Nerve Fibres and Ganglion Cells of the 

 Mammalian Retina.* — Dr. George Thin, in an article in the ' Journal 



of Anatomy and Physiology,' says that the isolation of the ganglion 

 cells and optic nerve fibres of the retina has certainly not been found 

 by histologists to be invariably an easy task, and he can testify from 

 experience that methods which are well fitted for the observation and 

 study of other parts of the retina, destroy the processes of the 

 ganglion cells and the nerve fibres. Max Schultze has acknowledged 

 this difficulty in his article on the r tina in Strieker's ' Handbuch,' 

 iniblished in 1872. Dr. Thin is induced, therefore, to believe that 

 the publication of a method by which he found the isolation of these 

 elements singularly easy, may be considered justifiable. 



The method holds good for the retina of the cat and the sheep ; 

 but there can be little doubt that it will prove equally useful in the 

 case of many other mammalia. His observations have been limited 

 to the eyes of these two animals. 



It is well known that if a sheep's eye be placed in a sufficient 



* ' Joui-n. Anat. and Phys.' (Humphry), xiii. (1879) p. 139. 



