that gives to the heterophil an appearance similar 

 to that of the eosinophil. 



The literature on the suLject of heterophils and 

 eosinophils reflects some of our present un- 

 certainties. The obsei-vation that aqueous 

 solution causes a degradation of rods is not new. 

 Bizzozero and Torre (1881) stated that if one 

 treats a blood preparation with water the white 

 corpuscles in question swell; the same thing hap- 

 pens to the rods themselves, which liecome pale 

 and at last disappear. They also found that 

 upon treatment with dilute citric acid the proto- 

 plasm of the white corpuscles laecomes swollen 

 and pale. The rods first draw together so that 

 there is formed a shining heap that hides the 

 nucleus. This heap very suddenly l^ecomes pale 

 and finally disappears. Although Bizzozero and 

 Torre recognized only four kinds of white blood 

 cells, they did include the true granular eosino- 

 phil as distinct from the rod eosinophil. Denys 

 ( 1887) writing on the Jjone marrow of pigeons 

 is less definite about the numljer of types of white 

 blood cells, does not distinguish between the two 

 eosinophils, and says it seems probable that most, 

 if not all, of those seen as dots are simply rods 

 viewed from the axis. 



Lundquist and Hedlung (1925) have pre- 

 sented a review of the subject and mention those 

 who believe the eosinophils in birds represent two 

 distinct types and those who consider that there 

 are only four kinds of leukocytes in birds. They 

 quote S. Henschen, who concludes that there are 

 two distinct types but who also mentions that post 

 mortem processes can cause the rods to go over 

 into granules. Lundquist and Hedlung's own 

 investigations led them to the unique opinion 

 that the granular eosinophil cell represents the 

 true condition and that the rods are artifacts, 

 produced at the time the smears are made. They 

 point out that the inclusions have the form of 

 granules after methyl alcohol fixation and of 

 rods after formalin or trichloracetic. In order 

 to follow the transformation from granules to 

 rods they diluted the blood in a white cell pipette 

 with 0.9-percent sodium chloride solution, which 

 was considered to be isotonic with chicken blood. 

 The diluent was allowed to act for 2 minutes be- 

 fore the blood mixture was put into a counting 

 chamber, then an eosinophil was obsei-ved in 

 order to note the form of granulation present. 

 After this, a solution of higher or lower concen- 

 tration was added to the side canal of the count- 



ing chamber and the changes in the cells were 

 followed. Usually filter paper was touched to 

 the fluid layer on the opposite side in order to 

 hasten the exchange. When the preparation was 

 diluted with water they found large, clear cells 

 with large, clear, scarcely visible round granula- 

 tions; when it was diluted with 0.7-percent 

 NaCl solution, all the granulations were round 

 and were larger than in the previous solution. 

 Preparations treated with 0.9-percent NaCl pro- 

 duced mostly round granulations in the cells, but 

 in a few cells these bodies took the rod form. At 

 lV2-percent NaCl concentration, the cells con- 

 tained rod-form granulations, and now and then 

 spherical granules. They summarize by saying 

 that in water the cells and granules swell and 

 become faint, but in 1.5-percent salt solution the 

 cells shrink and the round granulations are trans- 

 formed into the rod form. If not carried too far 

 these are reversible reactions, and thus the rod 

 eosinophil is an artifact brought about by osmotic 

 conditions. 



The chief reason why the interesting conclu- 

 sions of Lundquist and Hedlung have relatively 

 little value is that their study of cellular change 

 was made at the relatively low magnification re- 

 quired in using a counting chamber, and, al- 

 though they mention diese changes in the same 

 cell, it would seem rather difficult to keep a par- 

 ticular cell in the field during a rapid exchange 

 of fluids. 



Bradley (1937) examined the blood of numer- 

 ous birds and made observations similar to 

 our own. He reports (p. 995) that, "When 

 the color of the rod bodies has been partially 

 removed, . . . demonstration is made of darker 

 or lighter parts, giving the impression of deeply 

 stained granules along the paler length of the 

 body." In regard to technic he says (p. 997), 

 "Avian (fowl) blood is best stained by a method 

 which applies the eosin or related acid stain in 

 alcoholic solution and when the use of water or 

 saline solution forms no part of the process until 

 after the alcoholic stain has acted. 



"Adequate fixation before treating with water 

 or watery stain is no preventive for the destruc- 

 tive action of the latter on the rods. Water ap- 

 plied in moderation after staining is not detri- 

 mental to the result, and when left in contact 

 with the stained preparation for a longer time 

 is the means of showing up details of structure of 

 tlie rod bodies not otherwise appreciated." 



88 



