‘1 Man., 1898.] QUEENSLAND AGRICULTURAL JOURNAL. "915 
teaches that other methods of reproduction are not infrequent in the earlier 
stages of similar organisms. Such other forms have not, however, so far been 
seen in the organism under consideration. 
THE RELATIONSHIPS OF TICK FEVER. 
It has already been remarked that the points of resemblance and analogy 
between tick fever in cattle and malarial disease in man are remarkably 
abundant. The bovine malady has, indeed, been described as a disease of 
malarial type.* 1t may be of interest, therefore, to inquire how far this idea 
is supported by the observations which have just been recorded, and how far 
it is in accordance with some modern views as to the life history and mode of 
spread of the malarial parasite. It will be convenient to consider—first, the 
points wherein the life histories of the organisms of tick fever and malaria 
coincide or differ; second, the clinical and pathological resemblances of the 
two diseases ; third, the agencies by which each disease is communicated. 
THE RESPECTIVE ORGANISMS. : 
The life history of the tick fever organism is probably something as 
follows :—Beginning as a free spore consisting apparently of a morsel of 
undifferentiated protoplasm and (sometimes) a flagellum, it somehow makes it 
way into a blood corpuscle where it at first appears as a single amoeboid body. 
Then it divides into two (or more?) pear-shaped bodies (Pyrosoma bigeminum). 
Each of these eventually enlarges to form a crescent, in which spores are 
endogenously produced. The crescent becomes more or less spherical, and, 
rupturing, sets free a new crop of spores similar to those which formed the 
first stage of its developmental career. 
The malarial organismt in the blood of an infected person also com- 
mences its career as a free spore. It somehow makes its way into a corpuscle. 
There it at first appears as a single amwboid body.t This body undergoes 
certain developmental changes which result in its subdivision into a number of 
spores, which in due course are set {ree to commence the life cycle anew. In 
other cases the intracorpuscular amoebw, instead of at once passing into the 
sporulating stage, develop into crescentic§ or semilunar bodies which are 
probably the most constant and the most characteristic forms of the parasite 
as seen in human blood.|| Under certain conditions they are seen to undergo 
further developments 4—first into ellipsoids, then into spheres. From the 
latter are thrown out flagella processes which eventually become detached, and 
in this free state are believed by Dr. Patrick Manson to be the homologues of 
flagellated spores.** rom these facts it is evident that there exists a certain 
rough parallelism in parts at least of the life histories of the microparasites 
concerned in the two diseases. This is perhaps better seen in the accom- 
panying diagram. 
* Preliminary Observations on the Micro-organism of Texas Fever, by T. Smith, page 1. 
+ The varieties of the malarial organism corresponding to the various forms of the disease are 
not here considered. The general characters common to all forms only are referred to. 
The malarial amaba within the cells, unlike the corresponding form of the tick fever 
organism, often contains dark swarming pigment (melanin) granules. This phase of the malarial 
organism also grows to a larger size, and is paler and generally more actively amczboid in its 
movements. F 
§ The semilunars of Laveran are generally conceded to originate in this way. ‘The origin, 
nature, and destination of these bodies are still, however, more or less controverted points. 
|| Lhe malarial semilunars differ from the pyrosomal crescents in that they are present in the 
general blood stream (¢.g., from the finger), whilst the latter have only been found blocking the 
capillaries of internal organs, where, it may be incidentally remarked, they have probably much 
to do with the blood stasis observed in such situations. 
4] The developments in question are said by Manson to occur only in blood after it has been 
withdrawn from the human body ; they are never discoverable in specimens fixed the moment the 
film is spread. (Goulstonian Lectures, before Royal Col. Physicians of London, 1896; Lecture I.) 
** Surgeon-Major Ronald Ross found these flagella to be developed in the stomachs of 
mosquitoes from such crescents as they had swallowed with blood sucked from malarious patients. 
It is believed that they represent an alternative form of reproductive development designed for 
the perpetuation of the Plasmodium outside its human host, and would thus seem to lend colour 
to the suggestion, just now made, as to the possibility of some corresponding dimorphism in the 
reproductive phases of the Py7osoma in the bullock and the tick respectively, : 
Q 
