SOME HAKDEXIXG AGENTS. 375 



Muller's Fluid— as is well known — is composed of: — 

 Bichromate of Potassium ... ... 2 parts. 



Sulphate of Sodium ... ... i „ 



Water ... ... ... too „ 



It is the most useful, especially in the preparation of delicate 

 tissues, in which it fixes the protoplasm of the cells rather than 

 hardens them, and in this way causes but little shrinking of the 

 tissues, so that for congested organs, or mucoid tissues, it is invalu- 

 able, as also it is for the central nervous system, intestines, and 

 hollow organs. The great advantages of this agent are its liability 

 to harden large specimens thoroughly, even to whole brains ; its 

 power to penetrate, caused through the agency of the sulphate of 

 sodium, w'hich, if it once gets into the tissue, the bichromate of 

 potassium can follow. There is, as a rule, no danger of over- 

 hardening, and even if the process takes a considerable time the 

 results are almost invariably satisfactory. For delicate tissues it is 

 unequalled, and it is an essential factor in the special staining 

 processes of Weigert and Pal. 



It is said by some authorities (Wynter and Wethered, also by 

 Wethered) that it must not be used for micro-organisms in tissues, 

 nor foj; micro-chemical reactions as amyloid. I have examined 

 large quantities of material for both these conditions, and thus far 

 have experienced no difficulty ; Woodhead, Klein, or any other 

 author do not raise any such objections so far as I can learn. 



There is another exception. A deposit of lime salts is dis- 

 solved by this medium, and consequently chalky deposits, such as 

 occasionally occur in the glomeruli of the kidneys, are destroyed if 

 the organs be hardened in this way (Wethered), and also the 

 arterial walls are destroyed by chromic salts and thus escape 

 detection. I have hardened basilar, radial, and temporal arteries, 

 heart, aorta, etc., by Miiller and in chromic acid, in a case of 

 Arteritis Deformans^ and in calcific degenerations from other parts, 

 and found no difference. 



The disadvantages of Miiller's fluid are : — The colour given to 

 the specimen (but this can be removed by chloral hydrate), its 

 length of time to harden, a slight danger to grow mould or fungus, 

 which thus far I have never been troubled with, and which can be 

 avoided by using a little camphor, thymol, or naphthalin, and by 



