NOTES AND MEMORANDA. 191 



Deceptive Appearances produced by Reagents. — A paper recently 

 communicated by Dr. George Tbiu to the Royal Society * under this 

 title, was intended, in addition to being a contribution to the histology 

 of hyaline cartilage, to illustrate how much the apj^arent structure 

 of a tissue which is being examined microscopically depends on 

 methods of preparation. 



In the examination of a cartilaginous tumour of the lower jaw, 

 the author was able to isolate the cells from the cartilaginous sub- 

 stance of the tumour after the action of osmic acid. All the cells 

 observed were flattened, rounded, or somewhat polygonal bodies, with 

 round nuclei. Their contours did not correspond exactly with those 

 of the rounded cartilage " capsules " in which they lay. 



The examination of this tumour showed that most delusive appear- 

 ances as regards the nature of cartilage cells may be sometimes pro- 

 duced by staining and hardening agents. Carmine and eosin, by 

 staining an unformed substance that exists in the structure in defined 

 tracts, may simulate branched protoplasmic cells, and bichromate and 

 logwood preparations, either in sections or teased out, may as closely 

 simulate cells with fibre processes. 



These facts justify, the author considers, serious doubts as to the 

 correctness of interpretation in all cases in which histologists have 

 described branched cells in hyaline cartilage, whether the latter 

 existed as a normal structure or as a pathological growth. They 

 further show that, taken alone, carmine or eosin-staining should not 

 be held as conclusive evidence of the existence or limits of cellular 

 protoplasm in any animal tissue. 



Preparation of Red Blood-corpuscles.— Very excellent perma- 

 nent preparations of the red blood-corpuscles of Amphibia may be 

 made by Eanvier's method, as follows :— Some blood is allowed to 

 drop from a wound into about two hundred times its volume of a satu- 

 rated picric acid solution. After a few minutes the picric acid is 

 carefully poured off, leaving most of the corpuscles at the bottom of 

 the dish ; a solution of picro-carmine is then poured over them, and 

 allowed to stand a day or two. The picro-carmine is then poured off, 

 and the sediment put into acid glycerin (glycerin 100 parts, acetic 

 acid 1 part). The corpuscles so treated will last a long time, and 

 may be mounted in the acid glycerin at any time. The nuclei of 

 the corpuscles are stained bright red, and the body light yellow. 

 Corpuscles of Menohranchus, which are about twice as large as those 

 of the frog, prepared in this way nearly a year ago, appear perfect as 

 ever. 



Apparatus for Determining the Angle of the Optic Axes of 

 Crystals with the Microscope.— Professor A. de Lasaulx, referring 

 to a previous paper,J in which he described a method he had devised 

 for this object, says that it often presents difficulties, as it supposes 



* 'Proc. Roy. Soc.,' vol. xxviii. (1878) p. 257. 



t Mr. S. H. Gag.', in 'Amcr. Quart. Mic. Joiirn.,' vol. i. (1879) p. 160. 

 X 'Bulletin de la Socie'te Beige de Micro.scopie,' vol. iv. (1878) p. 177, noticed 

 in part in this Journal, vol. i. p. 207 



