8 ROYAL SOCIETY OF CANADA 



The following seem to be the only possible suppositions: 



(1) That the "dust-bodies" are imported from without, i.e., that 

 they are particles of dust or foreign matter derived from the air or 

 from the mechanical appliances used, 



(2) That they are fat, either already existing in the blood, or 

 imported there in the act of puncturing the skin. 



(3) That they are free leucocytic granulations — eosinophile 

 granules, gamma — or epsilon — granulations. 



(4) That they are destruction products (schistocytes) derived from 

 the red corpuscles, or that they are fragments of leucocytes. 



(5) That they are derived from the haematoblasts. 



(6) That they are fibrin. 



(7) That they are albuminous particles, precipitated from the 

 plasma. 



(8) That they are protozoa, micramœbas, malarial spores, or 

 bacteria. 



In view of the fact that the free particles in the blood present such 

 marked differences in size, shape, and colour, it may be inferred a priori, 

 with almost perfect certainty, that they vary in character and -originate 

 in at least more than one way. But, to determine the exact amount of 

 weight to be laid upon the various factors entering into the problem, 

 prolonged and careful observation of the blood is necessary, as well as 

 a study of the tinctorial and other microchemical peculiarities of the 

 '" dust-bodies." To arrive at anything like accurate conclusions, mot 

 only must a great amount of material be worked over, 'but also it must 

 be studied under a variety of conditions. 



To take up the various suppositions mentioned above seriatim, and 

 those most easily disposed of first. 



(1) That the "dust-bodies" are foreign matter imported from 

 without. 



The possibilities of error from this source can readily be avoided 

 if sufficient care be taken in the methods of technique. The needle or 

 lancet used in making the puncture should be sterilized in the flame; 

 the skin of the part to be punctured should be cleansed, first with water, 

 and then with a mixture of alcohol and ether; the first drop of blood 

 which exudes should be rejected; the glass slides and top-covers should 

 be thoroughly clean, and passed through the flame to remove grease; 

 the platinum loop for transferring the blood should be sterilized in the 

 flame; finally, any solutions or dyes should be carefully filtered and 

 then sterilized in the autoclave. In making the blood films all 

 manœuvres should be carried out quickly. When all these precautions 

 have been religiously carried out, the " dust-bodies " can still be demon- 

 strated. Again, that they are dust from the air is disapproved by the 



