182 



THE AMERICAN MONTHLY 



[October, 



masses, but the greater number are 

 formed most thickly around those 

 masses from which they often ra- 

 diate. 



If too much blood has been washed 

 away in preparation no formation of 

 fibrin will take place ; if in any part 

 of the field the blood remains thick 

 its edges will furnish the best area 

 for observation. 



For hardening and preserving 

 the plaques various other methods 

 were tried : — 



I. Hayem's solution. Dist. water 

 200, NaCl i,Na2 So^ 5, Hg„ CI 0.5. 



In using, dilute with J^ volume .75 

 Na CI. It does not act quite as quickly 

 as the osmic acid. 



3. Bizzozero's fluid. Na CI .75. to 

 which methyl violet has been added, 

 in ratio of i methyl violet to ^,000 

 Na CI. 



3. Preservation by drying both 

 spontaneously, and carefully over al- 

 cohol flame. Not satisfactory. 



Mounting media used were : — 



1 . Balsam and damar. Used di- 

 rectly with dried specimens or after 

 turpentine or xylol ; used also after 

 alcoholic staining, but not desirable, 

 as the alcohol causes shrinkage of 

 even osmic specimens. 



2. Glycerin. Not best for un- 

 stained plaques or osmic specimens. 

 Works well with stained specimens. 



3. Glucose. Very satisfactory for 

 temporary mountings. Used in con- 

 centrated aqueous solutions becomes 

 hard and requires no cement. 



4. Acetate of potash best medivim 

 effiployed. • In it both plaques and 

 fibrin threads stand out clearly and 

 sharply defined. 



5. Hayem's fluid preserves the 

 plaques several weeks ; but in speci- 

 mens several months old a granular 

 precijDitate is seen, and sometimes 

 crystals are deposited. 



Stainitig readily eflected by me- 

 thyl violet, gentian violet, and fuch- 

 sin, used in dilute solutions. 



Iodine irrigated under cover -slip 

 stains well, but the stain will wash 

 out in water after long treatment. 



Bismarck brown, magenta and Klein- 

 enberg's hEsmatoxylin and aqueous 

 hematoxylin best for permanent 

 stains ; acts slower. Anilin blue- 

 black, borax carmine, Frey's car- 

 mine and picro-carmine do not act^ 

 even in 34 hoin-s. 



The plaques may be chilled at once 

 on drawing to — 1° to + 2-!;° C, and 

 coagulation will not take place. The 

 plaque will retain its natural structure 

 for study, and may be observed to 

 change very slowly. 



Various opinions prevail as to the 

 origin of the plaque, summed as fol- 

 lows : — I . That they are young red 

 corpuscles ; 3, that they are derived 

 from red corpuscles ; 3, derived from 

 white corpuscles ; 4, nuclei floating 

 free in the blood ; 5, fibrin ; 6, glob- 

 ulin depositions from blood ; 7 5 that 

 they are independent elements. 



Dr. Kemp, after a summary of 

 opinion regarding these views, and 

 critical examination of the positions 

 of their adherents, concludes in favor 

 of the last, because — i , the plaques 

 are found with the other elements of 

 on drawing fresh into os- 

 3, thev have been seen 

 others circulating in the 

 there is no sufficient evi- 

 dence to prove that they are derived 

 from the red or white corpuscles and 

 are other than an independent mor- 

 phological element. 



The results of the work all go to 

 show that the breaking down of the 

 plaques is intimately connected with 

 the formation of fibrin. 



The granular masses formed by the 

 plaques become centres from which 

 the threads of fibrin radiate. The 

 threads are also deposited freely in 

 the field, and often as long, needle- 

 shaped bodies, but there is generally 

 a thicker deposit of fibrin in the im- 

 mediate vicinitv'^ of the granular 

 masses, especially the large ones, 

 than is noticeable elsewhere. 



The plaques, either before or after 

 breaking down, are not morphologi- 

 cally identical with fibrin, so that 

 they do not contribute as such to the 



the blood 

 mic acid ; 

 with the 

 vessels ; 3 



