METHODS OF EXAMINATION. 525 



the fever is produced by toxic bodies set free by the young 

 parasites, but that cannot yet be directly proved. The 

 presence of the parasites in the red corpuscles and the 

 destruction of their substance which takes place explain 

 the occurrence of the anaemia which so often results ; the 

 subsequent distribution and storage of the altered haemo- 

 globin producing the pigmentary changes in the various 

 organs. 



The disease can also be communicated from one person 

 to another by injecting the blood containing the parasites. 

 Several experiments of this kind have been performed 

 (usually about J to i c.c. of blood has been used), and the 

 result is more certain in intravenous than in subcutaneous 

 injection. In such cases there is an incubation period, 

 usually of seven to fourteen days, after which the fever 

 occurs. The bulk of evidence goes to show that the same 

 type of fever is reproduced as was present in the patient 

 from whom the blood was taken. 



It may also be mentioned that in certain affections both 

 of birds (as already referred to) and of reptiles, parasites 

 of somewhat similar character to those in malaria, though 

 of distinct species, occur in the blood of these animals. 



Methods of Examination. The parasites may be 

 studied by examining the blood in the fresh condition, 

 or by permanent preparations. In the former case, a slide 

 and cover-glass having been thoroughly cleaned, a small 

 drop of blood from the finger or lobe of the ear is caught 

 by the cover-glass, and allowed to spread out between it 

 and the slide. It ought to be of such a size that only a 

 thin layer is formed. A ring of vaseline is placed round 

 the edge of the cover-glass to prevent evaporation. For 

 satisfactory examination an immersion lens is to be pre- 

 ferred. The amoeboid movements are visible at the 

 ordinary room temperature, though they are more active on 

 a warm stage. With an Abbe condenser a small aperture 

 of the diaphragm should be used. 



Permanent preparations are best made by means of 

 dried films. A small drop of blood is allowed to spread 



