210 
POPULAR SCIENCE REVIEW. 
them for twenty-four hours in collodion. Each embryo is then arranged 
upon a small plate of elder pith soaked in alcohol and covered with a layer 
of collodion, and when the latter has arrived at the proper consistency very 
thin sections may be made through the embryo and the pith. They are to 
be preserved in glycerine. The process has the advantage of enabling one to 
see the precise point at which each section is made, and there is no occasion 
to free the sections from the collodion which encloses and holds them in 
place. — Ann. and Mag. Nat. Hist ., March, 1879. 
Preservation of Infusoria. — M. A. Certes has communicated to the 
French Academy of Sciences ( Comptes rendus, March 3, 1879) an account 
of a process which he describes as very successful in the preservation of the 
Infusoria. — He says that the preparations exhibited in illustration of his note 
showed u various species of Infusoria, fixed instantaneously in their form : 
the smallest details, cilia, cirrhi, flagella, buccal armature, can be observed 
under the highest powers; the green Euglence and Paramecin retain their 
characteristic colour. The nucleus and nucleolus, coloured artificially, stand 
out clearly, and show, when these occur, the curious phenomena so well 
described by M. Balbiani ” in 1862. A process offering such results as these 
is worth knowing ; the following is the author’s account of it. 
For the fixation of the Infusoria be employs osmic acid, either in the form 
of vapour, or in a solution containing two per cent, of the acid. In the 
former case the Infusoria placed upon a glass slide may by exposed to the 
vapour for from 10 to 30 minutes. With very contractile species he places 
a drop of the solution on the covering glass, before placing it upon the drop 
of water containing the animalcules. The excess of liquid under the cover is 
then removed by means of blotting paper, and thus a slight pressure, said to 
be advantageous, is produced upon the specimens. Two opposite sides of the 
thin glass are then luted down either with paraffine or with Canada Balsam, 
and the preparation being thus secured against displacement, the colouring 
material and the preservative may be introduced. M. Certes mentions 
soluble aniline blue and eosine as colouring agents, but gives the preference to 
Ranvier’s picrocarminate of ammonia, which he employs combined as follows : 
Glycerine 1 part. 
Water 1 „ 
Picrocarminate . . . . 1 „ 
In the introduction of glycerine the author follows the method recom- 
mended by Ranvier in his u Traite I Histologies He places in a damp 
chamber the preparations fastened as above described, and puts a drop of 
the coloured glycerine on the edge of the covering glass. The water evapo- 
rates very slowly, and in twenty-four hours the film of water between the 
glasses is replaced by dilute glycerine, which may in its turn be replaced by 
concentrated glycerine by the same process. The best varnish for closing 
these preparations according to M. Certes is dry Canada Balsam dissolved in 
chloroform. 
PHYSICS. 
Acoustic Vibrations Caused by Heat — Lord Rayleigh, in a recent lecture 
at the Royal Institution, drew attention to some forms of this phenomenon. 
