PRESEKVING AND PREPARING PATHOLOGICAL SPECIMENS. 61 



In many cases an excellent hardening is obtained by injecting the 

 preservative fluid through the blood-vessels. The lungs are well hard- 

 ened by pouring the fluid through the trachea into the air spaces. 



Finn-walled cysts of various kinds are well preserved in a condition 

 of distention by drawing off the natural contents through a fine canula 

 and refilling with, and immersing in, formalin solution. Delicate cysts, 

 such as echinococcus cysts, small embryos in their membranes, cystic kid- 

 neys, etc., may be preserved in a nearly natural condition in formalin. 



Kaiserling's Method of Fixing Natural Colors in Museum 

 Specimens. ' 



i. Fixation for one to five days in: 



Formaldehj'de . .... . . 200 c.c. 



Water . ... . . . . . 1000 " 



Nitrate of potassium . , . . .15 grains 



Acetate of potassium . . . . . . 30 " 



Change the position of the specimen frequently. The time of fixation 

 varies with the tissue or organ and size of the specimen. 



2. Drain and place in eighty-per-cent alcohol one to six hours, and 

 then in ninety-five-per-cent alcohol for one to two hours, to restore the 

 color, which is somewhat affected in the fixing solution. 



3. Preserve in: 



Acetate of potassium, . ... . . 200 grams 



Glycerin '.- . . 400 c.c. 



Water . ... 2000 " 



Since exposure to light reduces the color contrasts the specimen should 

 be prepared and kept in the dark. 



The Importance of Careful Fixation and Preservation. 



We would most urgently commend to the reader the importance of 

 putting pathological specimens which are to be hardened and subse- 

 quently examined microscopically, at the earliest possible moment into 

 the preservative fluids, which should always be abundant. Furthermore, 

 when specimens are large it is very desirable to cut them open, so that 

 the fluids may come into direct contact with the tissues. It should be 

 borne in mind that immediately after death or the removal of parts from 

 the body, especially in warm weather, changes commence in the tissues 

 and progress very rapidly, so that in some cases a few hours' or even a 

 few moments' delay will not only render subsequent microscopical exam- 

 inations difficult and unsatisfactory, but may lead to serious errors. Al- 

 cohol, and five-per-cent formalin are the most generally useful agents. 

 Carbolic acid and glycerine should not be used, even for the temporary preser- 



'See Mallvry and Wright: "Pathological Technique." 1901, p. 360. 



