tions put the proteins from the nucleus into sohi- 

 tion and in the wet condition they are spread 

 around tlie slide. These dry and later, when 

 stained, appear as long strands, irregular masses, 

 and fine filaments that take the typical nuclear 

 stain. If the slides are on edge, there will be 

 long streamers flowing downward. 



It has been found from experience that if blood 

 slides must be kept over until the next day before 

 staining, the rack should be put inside a glass dish 

 with a good cover and the edges sealed with ad- 

 hesive tape. No drawings have been made show- 

 ing these effects but there should be no difficulty 

 in recognizing them and in reproducing them. 

 If a slide held up to the light shows minute clear 

 areas punched out here and there over the smear, 

 those areas are a fairly good indication that flies 

 have had access to the slide. 



Squashed cells are exceedingly common in 

 avian blood (fig. 2, 6) . The part of the cell that 

 stains is the nucleus, and in the case of the cell 

 mentioned the cytoplasm has disappeared en- 

 tirely. When it has been squashed to this degree 

 it often becomes impossible to determine whether 

 it had been an erythrocyte, lymphocyte, mono- 

 cyte, or thrombocyte. If granulocyte cells be- 

 come broken they can be identified by their spe- 

 cific inclusions (figs. 175, 176, 187, 195, and 

 196). Broken monocytes can sometimes be 

 identified (figs. 148 and 149). 



Smudged cells are much more abundant in 

 bird than in mannnalian Ijlood, because, in birds 

 all blood cells are nucleated and there is much 

 more opportunity to find a smudged cell, than 

 where only the leukocytes cany nuclei, as in 

 mammals. 



It was noted by Furth, Seibold, and Rathbone 

 (1933) that in mice, smudged cells were rare 

 in normal animals but very numerous in cases 

 with lymphomatosis. They suggested that the 

 incidence of smudged cells might represent a 

 measure of the cells that were fragile, but they 

 knew of no way to put this idea to the test. They 

 were not found in the counting chamber. Al- 

 tliough no adequately controlled studies have 

 been made on chickens, the indications are the 

 same as for mice, that there are fewer squashed 

 cells from smears of normal individuals than 

 from those inoculated with tumor transplants. 

 Kyes (1929) found a certain proportion of 

 erythrocytes in fowl and pigeon so susceptible to 

 hemolysis that nucleated stromata appeared even 



when blood was diluted with the animals' own 

 serum. 



Smudged cells in chickens are so numerous 

 that it is easy to find all stages. The initial 

 reaction is liquefaction of chromatin which gives 

 the nucleus a light staining homogeneous appear- 

 ance, and the cjiiosome is flattened beyond its 

 usual limits. In anytliing beyond this initial 

 stage, the liquefied chromatin flows beyond the 

 nuclear membrane (fig. 58) and the cytoplasm 

 shows various stages of rapid disintegration. 



In most smudged cells the reaction goes all the 

 way and the nucleus is recognizable only as an 

 irregular, magenta-colored mass (fig. 2, 6). The 

 cytoplasm is less durable than the nucleus and 

 even when slightly flattened it loses its affinity for 

 the stain (fig. 60) . With only slightly more pres- 

 sure, the cytoplasm becomes almost completely 

 lysed (figs. 58 and 59) . When cells are severely 

 squashed, the nucleus also disappears and die 

 only indication that a cell previously existed is 

 found when some of the squashed material hap- 

 pens to overlie the cytoplasm of another cell (figs. 

 70 and 71 ) . Mere gossamer traces of squashed 

 chromatin can be seen between the cells but that 

 which falls on top of odier cells takes an intense 

 stain. In figure 70 the remains of the squashed 

 nucleus have taken the form of a row of bead- 

 like structures, and have interfered widi the 

 proper staining of the cytoplasm of the under- 

 lying cell. In figure 71 the nuclear substance 

 has iDcen stretched between two cells ; the cell to 

 the left received a bow-shaped strand extending 

 half way around the nucleus. The other por- 

 tion of the same squashed nucleus is only faintly 

 visible on the cell to the right, and a small por- 

 tion extends beyond the lower side. The vacu- 

 ole at the upper edge of the same cell is caused 

 by the presence of the squashed nucleus, which 

 interfered with the straining of the cytoplasm. 

 These small fragments of darkly stained material 

 tliat fall on the cytoplasm of normal cells are 

 confusing in that they may resemble foreign bod- 

 ies, parasites, bacteria, or even Cabot's rings. 

 Careful study may sometimes be necessary to 

 distinguish between such artifacts and some types 

 of pathogenic organisms. 



Two drawings of partially squashed cells from 

 Laboratory No. 2 (figs. 59 and 60) have been in- 

 cluded because they contribute some additional 

 information on several subjects — squashed cells, 



39 



