668 APPENDIX 



APPENDIX. 



FALLACIES IN BLOOD EXAMINATION. 

 Conditions leading" to fallacies may be dealt with in two classes: — 



(1) External. 



Insect hairs may simulate filariae. Low and Stiles took this view of 

 the F. gigas described by Proiit. 



Cotton fibres once led to a wholesale diagnosis of filarije cases. 



Care and cleanliness should exclude these. 



Films sent from the tropics may contain yeast cells or spores which 

 may cause considerable confusion. 



Less troublesome are pollen grains, animal and vegetable debris 

 found in the dust fouling the specimen. 



Films made from the blood of shot or slaughtered beasts or birds may 

 contain parasites carried from the gastro-intestinal tract, skin, hairy 

 hides or feathers of the cadaver. 



A piece of blotting paper may be used to dry one slide in staining 

 and in blotting a second with the same paper some of the parasites 

 from the first may be carried to the second slide. 



Flaws and cracks in the glass should always be anticipated, especially 

 as "seconds" are better than "firsts" for tropical work, as the best 

 quality slides "fog" readily. 



(2) Internal. 



Fresh Blood. 



Crenations of red cells are readily differentiated from parasites as a 

 rule. 



Vacuoles are a little more troublesome. They are highly refractive, 

 never show granules in their interior and exhibit no movements. 



Splits and cracks in red cells have received many names and as they 

 appear more frequently in pathological specimens they may be more 

 readily taken for hsematozoa. They have no amoeboid movement but 

 the contraction and the coagulation of the protoplasm may cause them 

 to change their position slightly. They have probably been mistaken for 

 bodies occurring in pernicious anaemia, leukaemia and lead poisoning. 

 The so-called Cropper's bodies may be of a similar nature. 



Granules from broken-down leucocytes may overlie red cells and 

 cause trouble. They are easily differentiated by focusing. 



A raised temperature may cause a peculiar degeneration of red cells 

 that must be watched. They are most often seen when one is working 

 with a hremostat. 



A blood platelet lying on a red cell may simulate a malarial Plas- 

 modium. These can soon be diagnosed by altering the light and by 

 focusing. 



Blood dust may be confused with granular debris from leucocytes 



