846 SUMMAKT or CUBRENT RESEARCHES RELATING TO 



glacial acetic acid. This preparation preserves Gonfervaa perfectly 

 without contracting the chlorophyll, to which it merely gives a 

 brownish tint. It presents one peculiar advantage in that it absorbs 

 the air-bubbles which objects often contain after being placed in the 

 cell. In this manner pith and fungi with numerous spores (Agarics, 

 Penicillium) which often retain, do what one may, a large number of 

 air-bubbles, can be prepared with success and without the necessity 

 of taking numerous precautions. A few days after the cell has been 

 closed, the air-bubbles, if not too numerous, will have disappeared. 

 Consequently, whenever washing in alcohol is inconvenient, this fluid 

 should be used. 



The acetic acid destroys the calcareous concretions which some- 

 times exist on the surface and even the interior of Algae. Bubbles of 

 carbonic acid are in this case given off, and for some days spoil the 

 appearance of the preparation, but they disappear before long. The 

 proportion of acid is pretty strong, but experience shows that a slight 

 excess of this acid is not injurious. 



No. 5. Camphor is dissolved in chloroform until it is saturated. The 

 superfluous camphor is as far as possible removed and fresh chloro- 

 form equal in amount to the fi.rst is added. Four grammes of this 

 solution is dissolved in a litre of distilled water ; no precipitate being 

 produced. 



This fluid may in most cases replace No. 1. It gives less trans- 

 parency to the preparations, but it possesses the advantage of but 

 slightly contracting the primordial utricle. For this reason it may 

 be employed for preserving even the most delicate marine and fresh- 

 water algfB, desmids, diatoms, with their endochrome, &c. For the 

 very delicate algas, such as the ConfervaB (Spirogyra, Bhynchonema, 

 &c.) preference is given to the following: — 



No. 6. 75 grammes of camphor-ivater, 75 of distilled water, and 

 1 of glacial acetic acid. This formula was invented by Dr. Ripart 

 and cannot be too strongly recommended. 



No. 7 is a gummy mixture for fixing the objects in the cells before 

 putting in the preservative fluid. Dissolve, cold, completely white 

 gum arabic in twice its weight of camphor-water, adding to the 

 solution, which is not perfect till the expiration of two or three days, 

 three-quarters of its weight of glycerin. It should be kept several 

 months in a long narrow bottle till the fluid has become completely 

 limpid through the deposit of the corpuscles which it at first holds in 

 suspension. 



No. 8 is a gelatinous mixture intended to replace Canada balsam. 

 Soak perfectly white gelatin in cold water for about twelve hours, 

 drain it, and set the vessel which contains it in warm water. When 

 it is melted mix an equal volume of glycerin with it. The mixture 

 solidifies on cooling. When required for use it is liquefied by 

 plunging the vessel containing it in warm water. 



No. 9. 500 grammes of distilled water and 1 of phenate of soda. 

 This fluid will preserve (in cells only) a host of vegetable tissues 

 and microscopical plants. The previous formulae are in general prefer- 

 able, but in cases where they do not answer this fluid may be tried, 



