93 



This is quite similar to M tiller's fluid in its action, and may be employed in the 

 same cases. It is generally used for the central nervous system. 



Harden in an abundance of the solution for 2-8 weeks, beginning with the 

 2% solution for 2-6 days, 3% solution 1-3 weeks, 5% solution 1-3 weeks. 

 Wash out in running water 24-48 hours. Place in 67% and 82% alcohols sev- 

 eral days, keeping in the dark meanwhile, changing when the alcohol is 

 colored. 



I 32. Chrome-oxalic (Graf). Formula: 8% aqueous solution of oxalic 

 acid, 4 parts ; 95% alcohol, 3 parts ; i% chromic acid, 3 parts. Mix the solu- 

 tions in the order given. 



Fix tissue in the solution 1-6 hours, wash in running water >-i hour, and 

 harden in 50%, 67%, and 82% alcohols. 



This appears to be a good general fixer for many organs ; it penetrates 

 well, the tissue cuts well after this method of fixation, and the staining is sharp 

 and strong. 



% 33. Alcohol. 95%, 67-70%, absolute 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% alco- 

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

 and likewise dehydrating (\ 41) preparatory to imbedding in paraffin or col- 

 lodion, affording thus a considerable economy of time. It is also most service- 

 able in pathological tissues where the presence of bacteria is suspected. In 

 some instances 67% alcohol answers as well or better, while in other cases ab- 

 solute (99%) alcohol should be employed. The addition of 5% glacial acetic 

 acid increases the penetrating power and improves the cutting quality of objects 

 containing much connective tissue. 



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

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

 ready for the next step of the imbedding process ($ 44 or 52). Stain as you 

 wish. 



\ 34. Formaldehyde. Solutions of this chemical have been found to be 

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

 and preserves -the natural transparency and pigmentation of the tissue, making 

 it valuable for gross anatomy and museum purposes. As a fixer, an aqueous 

 solution of 2-4% strength may be employed, or it may be used in conjunc- 

 tion with other chemicals, as picric acid, inpicro-formalin, or chromic acid and 

 acetic acid. 



Fix 12-24 hours, remove to 67% alcohol for a day, 82% alcohol one to 

 several days. Stain as you wish. 



$ 35. Perenyi's fluid. Formula : 10% aq. sol. nitric acid, 4 parts ; 95% 

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

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



Fix tissue for 4-5 hours, place in 67% alcohol for 24 hours, 82% alcohol 

 several days. 



| 36. Picro-nitric. Formula: Water, 95 c.c. ; nitric acid, 5 c.c. ; picric 



