PROGRESS OF MICROSCOPICAL SCIENCE. 37 



What is the exact Definition of Leucocyte and Pus-corpuscle'? — 

 The following is an account of an amusing discussion which took 

 place at a late meeting of the Philadelphia Pathological Society. 

 " Dr. Bertolet said he had not a clear idea of what was comprised by 

 the term ' leucocytes,' and desired much to know its limitations. 

 Dr. Tyson replied that, after other better-known histologists, he had 

 always used the word leucocyte in a generic sense, as including all 

 that class of small, round, variously granular cells which, according 

 to the situations in which they were found, were variously called 

 white blood-corj)uscles, mucus-corpuscles, young pus-corijuscles, or 

 the round cells of connective tissue, — in other words, dead amoeboid 

 cells. Dr. Bertolet said he thought this was an error in theory which 

 had been allowed to supplant practice ; that the white corpuscle and 

 pus-corpuscle were not the same. Dr. Eichardson said the word leu- 

 cocyte had been originally.introduced by Charles Eobin, who aj^plied 

 it to the class of bodies named by Dr. Tyson, whether alive or dead, 

 as well as to exudation-corpuscles, and he believed also, provisionally, 

 salivary corpuscles. He thought that if anyone would treat white 

 corpuscles contained in a drop of blood from his finger, first with 

 water by inti-oducing a small quantity at the edge of the thin glass 

 cover, and then with weak aniline solution, in the manner described 

 in his report on the white blood-corpuscle,* he would have no difficulty 

 in finding many globules which exhibited two or three, and occasion- 

 ally those which displayed four or five, well-formed and strongly-tinted 

 nuclei, and which manifested a precise identity, in that respect at 

 least, with the leucocytes of j)us, as described by older pathologists. 

 By this experiment it was easily demonstrated that the characteristic 

 formerly so much relied upon for the recognition of the pus-cell, and 

 quoted by Dr. Bertolet, — namely, that it possessed two, three, or more 

 nuclei, — was valueless as a means for its discrimination from the 

 leucocytes of blood. Dr. Tyson adxoitted that pus-corpuscles soon 

 became very granular from fatty degeneration, and then presented 

 objects which did not so closely resemble the white blood-corpuscle ; 

 but in their young state he did not think they could be distiBguished, 

 and to acetic acid and water both responded identically. Dr. Eichard- 

 son said that about one white corpuscle out of thirty is ordinarily 

 more granular than its companions, and he was strongly inclined to 

 think that these white corpuscles were also the seat of fatty degenera- 

 tion. The President said it was very important to have clear ideas as • 

 to the exact application of terms. He presumed, of coui-se, that this 

 discussion referred simply to the morphology, and not the vital 

 properties or developmental tendencies, of the cells in question. He 

 said that he himself had been called upon to study cases where in- 

 flammation had obKterated the trunks of vessels, — a matter which 

 brought up directly the question of being able to distinguish between 

 the corpuscles in the surrounding inflamed tissue and the white cor- 

 puscles which remained in the softened clots. By no means which 

 were available could he distinguish between the two. Dr. Eichardson 

 thought the more he studied the subject in connection with Cohn- 

 heim's observations, the more he was led to conclude that living leU" 

 * ' Amer. Mud. Assoc. Traus.,' 1872. 



