MIC KOSroPK'AI. DIAGNOSIS. f J 



needle to pierce it. We have tried this mixture and are highly 

 pleased with it. 



HARDENING. 



Hardening reagents act by coagulating the albumen and 

 gelatine in the tissues and by abstracting water. Among the var- 

 ious reagents used for this purpose there are two of general use; 

 alcohol and Miiller's fluid. 



As alcohol extracts the \vaterfromthetissuebesidescoagulating 

 the albumen and gelatine, it is very liable to shrink the specimen. 

 To obviate this shrinking as much as possible a small piece of 

 tissue should be first placed in dilute alcohol and gradually trans- 

 ferred to stronger solutions until the absolute alcohol is reached, 

 where it should remain until it is hard enough to cut. 



Miiller's fluid does not extract as much water as alcohol, but 

 acts on the albumen and gelatine. It is prepared as follows: 



Potassic bichromate, 2 parts, (or 2| parts.) 

 Sodic sulphate, i part. 

 Water, 100 parts. 



After this fluid has acted on the specimen for a few days it 

 should be removed and a fresh quantity added. 



At the end of -two weeks the specimen is transferred to alcohol 

 for a week or ten days, and then it is placed in absolute alcohol un- 

 til the hardening process is complete. 



Dr. Seiler uses a solution composed of equal parts of Miiller's 

 fluid, and 95 per cent, alcohol, claiming that large organs, as whole 

 kidneys, brains, etc., may be hardened throughout in a comparative- 

 ly short time. 



The working microscopist will soon become familiar with a large 

 number of other hardening reagents. 



SECTION CUTTING. 



But few specimens are in a suitable state in their natural con- 

 dition to be submitted to an examination. They must be either 

 teased or cut into thin sections. 



If it be so desired, sections can be cut from fresh tissues with 

 flat bladed scissors or with a Valentin's knife. For this purpose, 

 however, the freezing microtome is generally employed. The 

 s pecirnen is placed in the well of the microtome and by means of 



