FALLACIES AND PUZZLES IN BLOOD EXAMINATION 117 



and seeing if the body moves with, or independently of, the red cell, error may sometimes 

 be avoided. 



In the blood of cattle especially, platelets may assume strange shapes suggestive 

 of flagellates, but the fact that these thrombocytes always tend to unite in clusters 

 helps one to distinguish them. Botli in human and animal blood there is likely to be 

 more trouble with platelets in stained preparations {vide infra and Plate VII., fig. 2). 



At the same time a mass of platelets in human blood, surrounding a little dirt 

 which simulates pigment, may look very like a sporulating malarial parasite, but blood 

 platelets have ragged edges and one can nearly always have recourse to staining in a case of 

 this kind, while one should never dissociate the blood examination from the clinical 

 conditions. It is perhaps worth noting here that the latest work on the histogenesis 

 of blood platelets goes to show they are detached portions of the cytoplasm of 

 megakaryocytes, i.e. the giant cells of blood-forming organs (Wright). Swingle has 

 shown that blood platelets in blood ingested by an insect host may very closely resemble 

 herpetomonadiue flagellates and, from what I have seen, I believe errors can arise in fresh 

 blood if this fallacy is not borne in mind. It is, however, rather beyond the scope of 

 this paper to consider difficulties in connection with ingested blood. No one should take 

 up this study until he is in a position to grapple with the numerous problems which 

 assuredly await him. The same is true of the examination of blood from culture media. 



For those who seek to diagnose malaria from the presence of free spores in fresh blood, 

 a proceeding which Deaderiok emphatically condemns, the little dancing particles of blood- 

 dust or heemoconia may serve as a stumbling block. Personally, I do not think blood-dust 

 ever simulates parasites though it may be confused with granular debris from leucocytes, Hremoconi; 

 a matter of no moment, or with micrococci or fat droplets. The latter would appear not to 

 be an error, for, though Buchanan says they consist of fibrin, recent work with the 

 ultra-microscope by Neumann and others goes to show that they are really fat particles 

 possessing Brownian movement. They are more numerous after a meal and disappear 

 if the person or animal is starved. If neoessai-y, in the case of animals, this would furnish 

 a means of distinction. They may be absent in persons suffering from disorders of the 

 alimentary tract. Some of the appearances last described, and more especially blood-dust 

 and droplet degeneration of red cells, are much better seen with dark-field illumination, and 

 as the day will come when this method will be employed as a routine procedure, and also, in 

 all probability, as a method of differential diagnosis, some words on the appearance 

 of microscopic fields observed under this condition may not be out of place. The first thing 

 that strikes one is the enormous number of minute dancing particles. These vary in size 

 from about '2ft in diameter to the very tiniest specks which, being brilliantly illuminated, 

 look like infinitely minute sparkles. Crawley states that even with a magnification of 2,160 

 diameters some look only like tiny points of light. The larger particles vary in shape being 

 round, oval, rod, or dumb-bell shaped, and, while the smaller are solid, the larger may 

 appear vesicular. In these, which are highly refractile, one can sometimes see a central spot 

 of a ruby colour. This is mentioned by Porter. Crawley describes particles exactly like 

 blood-dust, which certain focussing tests and observations on their limited movements 

 apparently proved to be intra-corpuscular. I have never noticed these. He thinks some of 

 the blood-dust must therefore consist of broken-up erythrocytes or fragments derived from 

 them, but, personally, I do not see why fat particles by a process of osmosis might not 

 find their way into red cells. Indeed, in ordinary fresh blood films, viewed by transmitted 

 light, I have seen spherical bodies in red cells which certainly suggested oil globules. It is 

 worth noting that according to Love, ha>moconia are specially numerous in the blood 



