The sporogony of hæmogregarines is only known in a few cases, and in those affinity with the Coccidia is exhibited. In fact, the Hæmogregarines are now classified by some authors with the Coccidia.
(5) The Babesia or Piroplasma type. These are small parasites of red blood corpuscles of mammals. They do not produce pigment. They are pear-shaped, round or amœboid in Babesia, bacilliform and oval in other forms referred to this group. Piroplasms are transmitted by ticks. These parasites are described at length on p. [172].
Fig. 79.—Leucocytogregarina canis. Life-cycle diagram. Constructed from drawings by Christophers. (After Castellani and Chalmers.) Schizogony occurs in the bone-marrow. The parasite is transmitted from dog to dog by the tick, Rhipicephalus sanguineus, development in which, so far as known, is shown on the right.
THE MALARIAL PARASITES OF MAN.
Malaria, otherwise known as febris intermittens, chill-fever, ague, marsh fever, paludism, etc., is the name given to a disease of man, which begins with fever. It has been known since ancient times and is distributed over almost all the world, although very unevenly, but does not occur in waterless deserts and the Polar regions. In many places, especially in the civilized countries of Central Europe, the disease is extinct or occurs only sporadically, and large tracts of land have become free from malaria.
The rhythmical course of the fever is characteristic. It begins apparently suddenly with chilliness or typical shivering, whilst the temperature of the body rises, the pulse becomes low and tense and the number of beats of the pulse increases considerably. After half to two hours the heat stage begins. The patient himself feels the rise of his temperature (shown by feeling of heat, dry tongue, headache, thirst). The temperature may reach 41°C or more. At the same time there is sensitiveness in the region of the spleen and enlargement of that organ. After four to six hours an improvement takes place, and with profuse perspiration the body temperature falls rapidly, not often below normal. After the attack the patient feels languid, but otherwise well until certain prodromal symptoms (heaviness in the body, headache) which were not noticed at first, denote the approach of another attack of fever, which proceeds in the same way.
The intervals between the attacks are of varying length which permit of a distinction in the kinds of fever. If the attacks intermit one day, occurring on the first, third and fifth days of the illness and always at the same time of day, it is termed febris tertiana; if two days occur between fever days, it is called febris quartana. In the case of the fever recurring daily, later writers speak of typical febris quotidiana. But a quotidian fever may arise when two tertian fevers differing by about twenty-four hours exist at the same time (febris tertiana duplex). The patient has a daily attack, but the fever of the first, third and fifth days differs in some point (hour of occurrence, height of temperature, duration of cold or hot stage) from the fever of the second, fourth and sixth days. Similarly, two or three quartan fevers which differ by about twenty-four hours each may be observed together (febris quartana duplex or triplex); in the latter case the result is also a quotidian fever.
Two kinds of tertian fever are differentiated—a milder form occurring especially in the spring (spring tertian fever), and a more severe form appearing in the summer and autumn in warmer districts, especially in the tropics (summer or autumn fever, febris æstivo-autumnalis, febris tropica, febris perniciosa). The latter often becomes a quotidian fever.