came about because the nucleus aged and died 

 before the cytosome had reached its senility and 

 by the elimination of the nucleus, a longer life 

 span was obtained. 



The life span of erythrocytes among mammals 

 varies greatly, from 8 or 9 days for rabbits and 

 rats to about 100 days for monkeys ( Harne, Lutz. 

 Zimmerman, and Davis, 1945) ; for chickens it 

 is said to be about 28 days (Hevesy and Ottesen, 

 1945). In the pigeon after hemorrhage there 

 followed recurrent reticulocyte peaks at about 11- 

 day intervals (Graam, 1935). 



Another type of abnormal cell involves only 

 the nucleus and is illustrated in figure 3, 15 to 

 22, and figures 44-49. This defect was found 

 only in slides from Laboratory No. 2 and has 

 never been observed in any of the hundreds of 

 slides made at this Laboratoiy or in slides made 

 from farm stock. These cells are included here 

 because it is not known whether these abnormal 

 nuclei develop within the bird or appear on the 

 slide as a result of faulty technic. The pre- 

 ponderance of evidence points to an abnormal 

 cell. If this is true the cytopadiology deserves 

 thorough study since it is a very conspicuous han- 

 dle, or label, that the veterinarian could easily 

 use in the identification of a disease condition. 

 It is the type of abnormality tliat could be recog- 

 nized readily from field cases and requires only 

 low-power magnification to locate the cells. 

 Wirth ( 1950) in his figure 43 pictures cells show- 

 ing the same type of cleft nuclei. He labels 

 them pathological erythrocytes of birds but gives 

 no further information about them or the species 

 of bird in which they were found. It is possible 

 to go one step further than this and say that 

 it is not a breed difference since Laboratory No. 

 2 and this Laboratory are using the same breed, 

 namely. Single Comb White Leghorn. 



The defect appears as an achromatic or chro- 

 mophobic band across the nucleus; sometimes 

 it is narrow (figs. 3, 16. and 44) and sometimes 

 broad (figs. 3, 19 and 20, and 45) . Sometimes 

 it does not cut all the way through the nucleus 

 (fig. 3, 21). Sometimes it cleaves straight 

 across the middle (fig. 44) but frequently it is 

 diagonal (figs. 3, 17 and 18, and 45). Some- 

 times there are two clefts (fig. 46) and some- 

 times the ])reak is subterminal (figs. 3, 15 and 

 19, and 45) witli nuclear substance visible at 

 the tip, or it may appear as if the tip of the 

 nucleus had been lost (fig. 3, 22) . These achro- 



matic bands are not indentations because there 

 is usually enougli of the nuclear boundary still 

 visible to see that it is not curved inward. When 

 individual cells are examined closely there is no 

 evidence that the nucleus has been fractured and 

 the two portions pulled apart by pressure in 

 making the slide. 



Sometimes tlie chromophobic streaks extend 

 lengthwise in the nucleus (fig. 47) , leaving a cen- 

 tral axis of chromatin granules that stains nor- 

 mally. The washed-out band shows no trace of 

 chromatin granules; it shows only a faintly 

 stained linin network (figs. 47-49). These 

 three figures illustrate a transition leading to a 

 completely chromophobic nucleus. The late 

 stage (completely empty nucleus) might l^e con- 

 fused Avith the illusion of emptiness sometimes 

 found after Wright's stain on immature cells. 

 They are, however, different; the former is prac- 

 tically structureless and colorless but the latter 

 shows a pale blue color over the nucleus althougli 

 structural details are hardly visible. 



The chromophobic reaction might be a type of 

 chromatolysis but, if it is, it dift'ers from the com- 

 monly obsei-ved liquefaction process in that there 

 is a sharp boundary between the staining and non- 

 staining parts of the nucleus, whereas usually 

 chromatolysis is a progressive process affecting 

 all parts of the nucleus equally. 



Nuclear fractures are not limited to er^-thro- 

 cytes. In the same set of slides they were found 

 also in heterophils (fig. 3. 1) and in lymphocytes 

 (figs. 117-120). In the heterophil illustrated, 

 the clear areas extend lengthwise down the mid- 

 dle of two of the nuclear lobes. The nuclear 

 degeneration seen in lymphocytes will be de- 

 scribed later. It is usually more vacuolar and 

 irregular than in the erythrocytes, and rarely are 

 the clefts of uniform width, the fact that nuclei 

 of several different kinds of cells are affected 

 might be considered as evidence that this is a 

 technic artifact. If these chromophobic hands 

 are due to faulty technic, it would be expected 

 that some slides prepared at this Laboratory 

 would also show them, because certainly every 

 one of the manv thousands made here has not 

 been of top quality. Moreover. Laboratory No. 

 2 was asked several years later to prepare an- 

 other set from the same flock and stain them, and 

 none in the second set showed this particular 

 defect. 



Numerous visitors to this Laboratory who had 



32 



