THE INFECTIOUS DISEASES. 279 



BERI-BERI. 



Beri~beri is a disease of warm climates, believed by some observers to be infectious 

 in character, by others to be due to unsuitable diet. The lesions are often not well de- 

 fined. There are in some cases subcutaneous oedema and dropsy. There is often de- 

 generation of the peripheral nerves and of the heart and voluntary muscle. The bac- 

 terial studies which have been made upon beri-beri have not led to definite results. ' 



ACUTE RHEUMATISM. 



While the excitant of acute rheumatism is unknown there is much 

 reason to believe that it is an infectious disease. There are no charac- 

 teristic lesions; but various joints are frequently the seat of slight exu- 

 dative inflammation, serous or fibrinous in character. Albuminous de- 

 generation of the visceral cells with hyperplasia of the spleen has been 

 noted. The disease is not infrequently complicated by endocarditis or 

 pericarditis, by exudative inflammation of the lungs or pleura. Various 

 micro-organisms have been found in the body in acute rheumatism ; of 

 these the pyogenic cocci have been most frequently isolated, but these 

 are probably to be regarded only as excitants of the suppurative or 

 other complications. It is possible that more than one form of infection 

 is embraced under the designation rheumatism. 8 



MALARIA. 



THE EXCITANT OF THE DISEASE. 



The excitant of the disease long known clinically as malaria is a small 

 animal parasite, the Plasmodium malaria, which enters the red corpuscles 

 of the blood and in the course of its development destroys them. The 

 destruction of each cell is coincident with the maturation of its contained 

 parasite, which segments into a variable number of spores, or, more 

 properly, merozoites, a phenomenon which is also coincident with the 

 clinical appearance of the chill and its accompanying rise of temperature. 



These parasites of the red cell are protozoa belonging to a special 

 sub-group, the hcemosporidia. For purposes of description these hsemo- 

 sporidia of human malaria may be classified into three species or types, 

 each of which incites a different clinical form of , -ddseaseVand each of 

 which also differs from the other types in its morphology/ These types 

 are the tertian, the quartan, and the sestivo-autiimnal parfsites. 



Tertian and Quartan Types. If the blood of a patient suffering from 

 tertian fever be examined shortly after a chill, a number of the red 

 cells will be found to contain small, highly refractile, actively amoe- 

 boid bodies which are the early forms of the plasmodia or merozoites. 



1 For bibliography of beri-beri see Sodre, "Twentieth Century Practice," Bd. xiii. 



2 For summary of the bacteriology of Rheumatism see Poynton and Payne, The 

 Lancet, Sept., 1900, pp. 861 and 832; also Poynton, Practitioner, vol. Ixv., p. 22, Jan., 

 1901. 



