ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 149 



j8. Collecting, Mounting and Examining Objects, &c. 



Mounting and Photographing Sections of Central Nervous 

 System of Reptiles and Batrachians.* — Dr. J. J, Mason describes 

 the methods he employed in mounting the sections from which the 

 plates illustrating his book "j" were " artotyped," 



" Both the brain and spinal cord were entirely separated from the 

 body, and, with their membranes, placed in iodine-tinted alcohol 

 until they had acquired a slight degree of consistency — from six to 

 twelve hours. They were then transferred to a 3 : 100 solution of 

 bichromate of potash, with a small piece of camphor, in a tightly 

 corked wide-mouthed bottle, and allowed to remain until ready for 

 cutting, renewing the solution every two weeks. 



The time required for the hardening process varies considerably 

 in different animals, and this variation is more dependent upon the 

 class of animal than upon the relative dimensions of the specimens. 



For example : on the same day I placed the brain of a large rattle- 

 snake with that of a small salamander in the same bottle, and at the 

 end of six weeks the former was ready for section, whilst the latter 

 was not sufficiently hard until a month afterwards. By thus em- 

 ploying the same reagent in all cases, I have been able to note 

 constant differences in the action of both the hardening and the 

 colouring agent, carmine. 



Perhaps the most striking illustration of this is furnished by 

 the nervous centres of tailed batrachians, which, while they stain 

 very readily, invariably require about a third more time to harden 

 than specimens from the other orders. Specimens from ophidians 

 stain less satisfactorily than those from any other of the classes which 

 I have studied, while with the spinal cords of alligators, turtles, and 

 frogs failure to obtain good results in this particular is very rare. 



In all cases the sections have been stained after cutting, injury 

 from excessive handling being wholly avoided by the use of siphon- 



* ' Minute Structure of the Central Nervous System of certain Reptiles and 

 Batrachians of America,' 1879-1882. Cf. iii. (1883) p. 910. 



t " The methods of histology have reached a perfection which is building up 

 new departments of knowledge, and among successful pioneers in these labours 

 Dr. Mason will always hold an honoured place for the technical skill with which 

 he brings the reader face to face with the revelations of his Microscope, and for 

 the sumptuousness with which his work is given to the world. No such mono- 

 graph has previously come under our notice, for the illustrations of a difficult 

 research leave nothing to be desired. , . . 



" No words could do justice to the beauty of the plates or the value of the 

 information they convey ; and it is not too much to regard this work as opening 

 a new era in research by substituting knowledge of facts of microscopical 

 structure for their interpretation by the hand of artist or author ; but we can 

 scarcely hope to see many books so beautifully illustrated. The author's method 

 has the merit of inaugurating a comparison of the minute anatomy of the nervous 

 system by enabling the reader to see the structures which he has discovered as 

 he saw them ; and hence the book will always be a valuable work of teference ; 

 and it will certamly induce others to hand on the torch of knowledge in a like 

 excellent way." — Prom Bibliographical Notice in Ann. and Mag. Nat. Hist., xii. 

 (1883) pp. 270-4. 



