MEDICAL WORK WITH MICROSCOPE 



have blood parasites resembling minute eels with 

 long threadlike tails. These parasites are the cause 

 of the malady and are introduced into the blood by 

 flies, closely related to house flies. There are a very 

 large number of blood parasites of one kind and 

 another, so it is clear that a knowledge of blood is 

 very important to the medical man. 



From our remarks concerning the sizes of the red 

 corpuscles in the blood of man and various animals, 

 one might be excused from thinking that it would 

 be quite easy for anyone with a little experience 

 to recognise human blood. As a matter of fact it 

 is very difficult, it is always a doubtful matter to 

 rely upon size alone. We have mentioned blood 

 crystals and these give us a slightly better clue to 

 the origin of the blood, for the blood crystals of 

 different animals vary in shape, far more than their 

 corpuscles. Those of the guinea-pig, for example, 

 are little four sided pyramids; those of the mouse, 

 eight sided and so on. Some apes, however, have 

 blood crystals very similar to those of man, so 

 similar that the two may be confused. The micro- 

 scopist who is compelled to give an opinion con- 

 cerning the origin of a sample of blood, especially 

 blood which is some days old, is faced with no light 

 task. 



Without the assistance of the microscope, medi- 

 cal men would never have discovered the cause of 

 many of these insect-borne diseases, they could 

 never have traced the development of the blood 

 parasites in the bodies of insects. For many years 



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