[88] 



a mew ffftctbob of {preparing flDinute 

 flDicroecopic ©roaniema* 



IN a recent German periodical, the " Zoolog. Anzcigcr^'' vol. 4, 

 Professor G. Entz describes the method used by him in 



momiting minute organisms for the microscope, such as 

 Protozoa, Rotifera, Infusoria, etc. He first enumerates some of 

 the plans which have been previously tried, referring especially 

 to the mounts exhibited by Duncker in 1877, which showed 

 numerous fine details in a most wonderful manner, but unhappily 

 were not permanent. He then goes on to say that, according 

 to his experience, there are various means well adapted for fixing 

 the smallest and most delicate organisms — such, ^.o-., as pyroligneous 

 acid, picric acid, chromate of potash in glycerine, etc. — but that 

 a preparation strongly recommended by Ur. Paul Mayer for the 

 lower animals — viz., picro-sulphuric acid — should certainly have 

 the preference over all others. This is prepared, according to 

 Kleinenberg's formula, as follows : — 



100 parts, cold saturated solution of picric acid in water ; 

 2 parts, strong sulphuric acid. 

 Mix well together, and filter ; and when diluted with three times 

 its bulk of water, it is ready for use. One great advantage of this 

 medium is that it supplants the water and other fluids in the 

 animal's body ; and after having done its work, allows itself to be 

 entirely removed and replaced by alcohol. With large objects, a 

 sufficient quantity of it must be used, and generally it is needful 

 to open the body well with a pair of scissors, so that the liquid 

 may penetrate more thoroughly, as it passes with difficulty 

 through thick chitinc. It must be used before or immediately 

 after death, — time not being allowed for the blood or animal- 

 juices to coagulate and fasten the organs together ; neither, of 

 course, should it be employed for animals containing carbonate 

 of lime, where that is desired to be preserved. 



But its principal use in the hands of Professor Entz is for the 

 preservation of minute organisms, as already mentioned. These 

 it kills instantaneously, without injuring their structure, and 

 fixing the smallest details as in life — even flagella and cilia, the 

 suctorial disks of the Acinetae, or the pedicels of rapidly-jerking 

 Vorticell?e. Rotifers, such as Carchcsium and Epistylis, may 

 often be fixed in the act of lively rotation, though they generally 

 die with the peristomes moderately withdrawn. Infusoria may be 

 caught in the act of fission or conjugation; and nucleated 



