QUARTERLY CHRONICLE. 133 
The paper contains an interesting comparison of the 
author’s results with respect to the retina with those of 
previous writers, as Leydig, Keferstein, Krohn, and Babu- 
chin, who have investigated the structure of the eye in 
the Mollusca, and concludes with some excellent general 
observations on the relations of the eye and its different parts 
to the nervous centre, and with a copious table of comparison 
of the various parts of the organ of vision in the Vertebrata 
and various Mollusca, as the Cephalopoda dibranchiata— 
Nautilus, Pterotrachea, Helix, Pteroceras, Pecten, and Asterias. 
3. * On the Use of Creosote in the making of Microscopic 
Preparations,” by Prof. Dr. Ludwig Stieda, of Dorpat.— 
Acknowledging the value of the method proposed by Mr. 
Lockhart Clarke for the preparation of transparent sections 
of the organs, and especially of the nervous system, consist- 
ing, as is well known, essentially in the immersion of the 
sections first in absolute alcohol and afterwards in oil of 
turpentine, and then mounting them in Canada balsam, Dr. 
Stieda points out some of the inconveniences with which, as 
he thinks, this mode of procedure is attended. Amongst 
these he enumerates the loss of time attendant on the double 
immersion, and the difficulty, while immersing a series of 
sections in the alcohol, of preventing their becoming confused. 
In order to obviate these supposed objections he has, he says, 
been for some time in the habit of at once treating the 
sections with oil of turpentine without any previous dehydra- 
tion by alcohol—a modification of the Clarkean method, 
which was first proposed by Reissner; but, from what is 
said, it is difficult to perceive that it has any advantage over 
the original proposal, and, in fact, to be attended in most 
cases with a great waste of time. 
More recently Rindfleisch has recommended instead of oil 
of turpentine the use for the same purpose of oil of cloves. 
This oil requires that the preparation need not be immersed 
in alcohol for more than about two hours instead of twenty- 
four. And one recommendation of it, according to the pro- 
poser, is that, as the preparation is rendered transparent 
much more quickly than by turpentine, the glass cover may 
be more speedily applied, and thus the risk of contraction of 
the specimen avoided. According to Dr. Stieda, all the advan- 
tages assigned by Rindfleisch to oil of cloves are obtained in 
a higher degree by the use of creosote, a medium first pro- 
posed by Kutschin in his “ Researches on the Structure of 
the Spinal Cord in the Lamprey.’* 
Kutschin’s method, after placing the section upon the 
slide and remoying the superfluous water, consists in applying 
* ‘Diss Inaugural.’ Kasan, 1863. 
