14 



21. Picro-nitric. Formula: Distilled water, 95 c. c.; nitric acid (strong), 

 5 c. c.; picric acid, to saturation. Only to be recommended for eggs rich in yolk 

 and where a high power of penetration is required. 



Fix 4 to 12 hours, transfer to 67% alcohol, 1 day 82% alcohol several days 

 changed frequently. It is necessary to wash out thoroughly which is accomplished 

 however, with difficulty. 



22. Perenyi's fluid. Formula: 10% aq. sol. nitric acid, 4 parts; 95% 

 alcohol, 3 parts; K% aq. sol. chromic acid, 3 parts. An embryological fixer 

 of much value. It is also serviceable for general work. 



Fix tissue for 4 to 5 hours, place in 67% alcohol for 1 day, 82% alcohol several 

 days. 



23. Alcohol. 95%, 67 or 70% alcohol. The employment 



of most of the fixers so far mentioned requires the expenditure of considerable 

 time, rendering them inapplicable or unsuitable in many instances. 95% alcohol 

 itself answers admirably for most histologic objects, fixing well, hardening and 

 likewise dehydrating ( 49) preparatory to imbedding in paraffin or collodion, 

 affording thus a considerable economy of time. It is also most serviceable in 

 pathological tissues where the presence of bacteria is suspected. In some instances 

 67% alcohol answers as well or better, while in other cases absolute (99%) alcohol 

 should be employed. 



Fix in 95% alcohol for 1 to 3 days, changing two or three times, after 3 or 4 

 hours and after 24 hours. The tissue will probably be found to be dehydrated 

 and ready for the next step of the imbedding process ( 51 or 62). Stain as you 

 wish. 



24. Alcohol-acetic. The addition of 5% glacial acetic acid to 95% 

 alcohol or absolute alcohol increases the penetrating power and improves the 

 cutting quality of objects containing much connective tissue. The following 

 formula possesses high penetration and is sometimes useful: 



25. Alcohol-acetic (Carnoy's fluid, 3-1). Formula: Glacial acetic acid 



1 part, 95% or absolute alcohol, 3 parts. Transfer after fixing to 95% or absolute 

 alcohol, changing each day until the acetic acid is well washed out. 



26. Chloroform-alcohol-acetic. (Carnoy's 6-3-1 ). Formula: 95% or 

 absolute alcohol, 6 parts; chloroform, 3 parts; glacial acetic acid, 1 part. Fix 



2 to 24 hours or longer, transfer to 95% alcohol, changed two or three times. 



27. Carnoy's Sublimate mixture. The above ( 26) with mercuric chlorid 

 added to saturation. A very penetrating and excellent fixer, particularly useful 

 for nuclear preservation and for embryos. 



Fix 1 to 24 hours, transfer to 95% alcohol for 1 day, then to 82% alcohol for 

 several days, changing daily and adding iodine solution (11) until the excess 

 mercuric chlorid is removed. 



28. Alcohol-acetic-formol. Combinations such as the following are 

 useful for general purposes. V. Luko's formula: Alcohol, 67%, or 82%, 100 c. c. 

 glacial acetic acid, 5 c. c.; formalin, 5-10 c. c. 



Fix for 12 to 24 hours or longer; remove to 67% or 82% alcohol for 1 day 

 or more. 



29. Formaldehyde. Solutions of this chemical have been found to be 

 good preservatives and hardeners and fairly good fixers. It penetrates rapidly, 



