88 BACTERIOLOGY 



membranous ulceration of the mouth and throat, not at all 

 uncommon in this country, especially among children, known 

 as Vincent's Angina, is characterised by the presence of a 

 Spirochaete in association with a peculiar spindle-shaped 

 organism, B. fusiformis (see Frontispiece, fig. 20). The exact 

 position of these organisms in the scale of classification is 

 still more or less undetermined. 



Some spirochaetes, including the organism of syphilis, have 

 been recently successfully cultivated, and it is possible that a 

 diagnostic test the luetin reaction analogous to the tuber- 

 culin and mallein tests, will now be available in the case of 

 syphilis. 



Malaria Parasites. The organisms which cause Malaria 

 in the human subject belong to a group of the Class Sporozoa 

 known as the Haemosporidia, all of which are blood-parasites 

 which usually possess two specific hosts the one usually a 

 vertebrate such as man, in whose body an asexual cycle of 

 development by fission or schizogony occurs, corresponding 

 in its periodicity with the attacks of the fever ; and another 

 invertebrate host, usually a biting fly of the mosquito tribe, 

 in which a sexual cycle or sporogony is completed. These 

 two life-cycles are very complex, and were first worked out 

 with much patient labour by Bonald Ross in a form of bird 

 malaria. There is still a good deal of variation of opinion as 

 to the exact nomenclature and classification of the malarial 

 parasites of man. At least three types of malaria are recog- 

 nised, and their parasites, which possess many synonyms, are : 



Plasmodium yivax, the cause of Benign Tertian Malaria, 

 with a life-cycle in man of about forty-eight hours, the attacks 

 occurring every second day. 



Plasmodium malariae, the parasite of Quartan Fever, in 

 which the attacks come on every third day. 



Plasmodium immaculatum (or Laverania malariae), the 

 cause of Tropical, Pernicious, or Aestivo-Autumnal, or 

 Malignant Tertian Malaria. 



These three parasites are distinguished by their morphology 

 and by their pathogenic effects upon their host. Each has a 

 somewhat similar developmental cycle. In man, a young 

 parasite, which is amoeboid, fastens upon and enters a red 

 blood-corpuscle in which it grows and upon the substance of 

 which it feeds. It then goes on to form (1) a rosette-like body 

 which proceeds to divide into small spherical bodies, the red 

 corpuscle is destroyed, and these small parasites are freed into 

 the blood (this phase corresponding to the acute attack or 

 paroxysm of the fever), and invade fresh blood-corpuscles ; 



