1 882.] in the Zoological Station in Naples. 699 



the organs together. A large quantity of the fluid should be used, 

 and it must be changed as often as it becomes turbid. The same 

 rule holds good in the use of all preservative fluids. It is well 

 also, especially with larger objects, to give the fluid an occasional 

 stirring up. 



In order to avoid shrinkage in removing small and tender 

 objects from the acid to the alcohol, it is advisable to take them 

 up by means of a pipette or spatula, so that a few drops of the 

 acid may be transferred along with them. The objects, sinking 

 quickly to the bottom, remain thus for a short time in the medium 

 with which they are saturated, and are not brought so suddenly 

 into contact with the alcohol. In a few minutes the diffusion is 

 finished ; and they may then be placed in a fresh quantity of alco- 

 hol, which must be shaken up frequently and renewed from time 

 to time until the acid has been entirely removed. 



The sulphuric acid contained in. this fluid causes connective tis- 

 sue to swell, and this fact should be borne in mind in its use with 

 vertebrates. To avoid this difficulty Kleinenberg has recom- 

 mended the addition of a few drops of creosote, made from beech- 

 wood tar, to the acid. According to Dr. Mayer's experience, 

 however, the addition of creosote makes no perceptible difference 

 in the action of the fluid. 



This fluid must not be used with objects {e.g., Echinoderms) 

 possessing calcareous parts which it is desired to preserve, for it 

 dissolves carbonate of lime and throws it down as crystals of 

 gypsum in the tissues. For such objects picro-nitric acid may 

 be used. It is prepared as follows : 



ricro nitric acid also dissolves carbonate of lime, but it holds 

 it in solution, and thus the formation of crystals of gypsum is 

 avoided. In the presence of much carbonate of lime, the rapid 

 production of carbonic acid is liable to result in mechanical 

 injury of the tissues, hence in many cases chromic acid is prefer- 



Picro-t 



: respects, an excellent preservath 



tedium, and as a rule will be found to be a good alternativ 

 those cases where picro-sulphuric acid fails to give satisfactory 



