Blood Plasma in Imbedding Small Organisms. 173 



such as a protozoon, through the numerous reagents necessary 

 for imbedding in paraffine preliminary to microtome sectioning. 

 It has been found that the phenomenon of coagulation in blood 

 plasma makes it of use in work of this type. In carrying out 

 this method, a few drops of blood plasma is placed on a depression 

 slide under a binocular microscope and the specimen at once 

 placed in it with a pipet. After the plasma coagulates, which 

 will take place in a very few minutes, the specimen will be found 

 to be firmly imbedded in a resistant fibrin clot which can be taken 

 through the various reagents, imbedded in paraffine, sectioned in 

 any desired plane and finally mounted on a slide. In brief, the 

 clot containing the specimen may be treated as a regular piece of 

 tissue of the same size. 



The orientation of the specimen in the clot may be accom- 

 plished before the clot is fully formed or at the time when the 

 clot is in the clearing fluid just prior to imbedding. In the 

 clearing fluid the clot becomes transparent and can be examined 

 under a microscope and the imbedded specimen located in it. 

 The clot can then be trimmed so as to indicate the orientation of 

 the specimen. 



Plasma of various animals can be used. I have generally 

 used frog plasma and have secured it by the method previously 

 described. 1 



Blood plasma has also been found to be useful in holding 

 small animals firmly in a certain position so that they can be 

 dissected. In this connection it may be noted that the dissection 

 can proceed as far as desired and then no matter how fragile 

 the dissected parts may be, additional plasma can be added and 

 the fragile dissected part or parts imbedded in a clot in the same 

 manner as described above. If desired, the clot can then be 

 taken through the regular reagents and imbedded in paraffine for 

 sectioning. 



There is no doubt that blood plasma can be put to many other 

 similar uses depending upon the nature of the problems and the 

 ingenuity of the investigator. The securing and keeping of the 

 plasma will not be found too difficult after the operation has been 

 performed a few times. 



1 Journal of Experimental Medicine, 1915, xxi, 456. 



