THE WOMBAT. 



Formalin is water in which 40 per cent, of this aldehyde 

 is contained. All percentages of formalin, or formol, mentioned 

 by any writer, therefore, are not to be considered as percentages 

 of formic aldehyde, but as percentages of 40 per cent, of the 

 aqueous solution of that product. (You must note the difference 

 between formalin solution and formalin. The strength of 

 " Formalin Solution " is 1 oz. of formalin to 8oozs. of water, 

 and so is only \\ per cent. It is sold in this way for disinfect- 

 ing purposes, and is not strong enough for general purposes 

 of preserving tissues). Formalin is colourless and neutral, 

 and has a pungent and penetrating odour. The fumes are 

 said to be not harmful unless inhaled for some hours. It is 

 important to remember that it is very volatile, and must be 

 kept in tightly-closed vessels, or the strength will diminish. 

 I have estimated the specific gravity to be i.o78. It is free 

 from corrosive properties, and is not poisonous or combustible. 

 It is a most powerful antiseptic agent. I have seen it noted 

 that Drs. Stahl, Berlioz, and Trillat proved that in a dilution 

 of 1 to 50,000 it killed anthrax bacilli. It is, therefore, as 

 powerful in this respect as corrosive sublimate. But enough 

 on this head. 



Now, as to its use in preserving animals and plants. For 

 general purposes I consider the best strength is between 5 and 

 10 per cent., certainly no stronger. I have many successful 

 examples in which I have used only 2 per cent, strength, but 

 I have also had a few failures with it. I think 5 per cent, 

 will be found strong enough for nearly all substances, provided 

 it is changed to a fresh supply after the first day or two of 

 treating a specimen ; and in larger specimens it should be 

 changed every day for a longer or shorter time, according to 

 the size of the specimen, or, failing this, a drop or two of 

 formalin should be added occasionally, according to what the 

 tissue is, to make up the loss of strength occasioned by mixture 

 with the water of organization. 



You will notice from my specimens that it preserves 

 animal structure without causing any perceptible shrinkage, 

 nor does it coagulate the albumen, as alcohol does, by extract- 

 ing the water from the tissues. The colour of the blood in 

 tissues changes to a brownish shade, but may be restored at 

 any time by immersion in strong alcohol. 

 {To be Continued.) 



THOS. PERRY <&5 SON, 

 Gunsmiths, Locksmiths & CJeneral Machinists. 



Scales St Weighing Machines Repaired & Adjusted. Metal Turning & Screw Cuttins 



RYRIE STREET BAST, GEEI.ONG. 



