REVIEW — TROPICAL MEDICINE, ETC. 149 



Of special interest is the work of Koch' on the development of the parasite in Piro- 

 the tick. His observations were made on P. bigemiHum and P. parviim of bovines. The plasmosis — 

 process only occurs in adult females which have gorged themselves with blood. The changes contimud 



begin after 12 to 20 hours in both species when the parasites leave the erythrocytes and lie 

 in heaps. Some develop spcar-like processes and become club-shaped. These spears 

 resemble pseudopodia. Two chromatin granules are seen at the thick end of the XDarasite. 

 The spears become less numerous and the parasites more rounded. Thoy grow and acquire 

 a membrane. Amoeboid bodies are developed which break up into rounded parasites each 

 with a chromatin mass. Similar forms were seen in the eggs of the tick. Kleine^ found 

 somewhat similar changes in Babesia canis kept in defibrinated blood mixed with normal 

 saline. 



Koch's observations have been confirmed and extended by Christophers/ who worked 

 with Piroplasma canis in India. As regards the developmental cycle in the tick, he 

 concludes : — 



1. In B. satiguineus there are two means by which infection is transmitted. 



(a) Hereditarily through the egg. A method shown both by experimental infection of dogs and observation 

 of the parasite in the tick. 



(b) Stage to stage infection. Not yet proved by experimental infection, but practically certain from 

 observations upon the parasite. 



2. In both methods of infection the parasite goes through the same cycle of development, becoming in turn 

 a club-shaped body and then a zygote which breaks up into " sporoblasts," and these again into " sporozoits." 



3. In hereditary infection club-shaped bodies originating each from a single parasite penetrate the ova 

 either in the ovary or in their passage down the oviduct, and in the yelk become zygotes. In the larva the 

 zygotes have broken up into sporoblasts which are found disseminated in the tissues, and in the nymphs the 

 sporozoits have accumulated in large numbers in the salivary glands. 



4. In infection from nymph to adult the club-shaped bodies, after being formed in the gut of the nymph, 

 penetrate cells of the embryonic tissue which will eventually form the adult, and embedded in the cells of this 

 they become zygotes. The sporozoits derived from these zygotes may find themselves, without any action on their 

 part, in salivary cells or they may be situated elsewhere, in which case they probably reach the salivary cells by 

 their own movements, possibly aided by the circulation of fluids in the tick. 



The details of development strongly suggest a cycle of a sexual nature, and, if this be the case, the sexual cycle 

 of piroplasma has many points in common with the sexual cycle of the malarial parasites and proteosoma. This 

 has been already pre-supposed by the nomenclature employed which it seems reasonable to use until further 

 research either confirms or shows it to be untenable. 



The greatest difference between the development and that of the malarial parasite occurs in the pecuKar 

 dissemination of the sporoblasts and sporozoits, and the fact that the ookinete (?) comes to rest not in the gut wall 

 but in the tissues. That the malarial zygote has no true wall of its own has been already supposed by Qrassi, and 

 in this the zygote of piroplasma would bear it a resemblance. The separation of sporoblasts by the growth of the 

 embryonic tissue, and possibly by the movements of the sporoblasts themselves and the infiltrating action of 

 piroplasma, have, so far as I know, no parallel in malaria or other of the pathogenic protozoa. The sporozoits, 

 except that they have not the filiform shape of those of malarial parasites, seem to correspond exactly to these and 

 their eventual location in the salivary acini is exactly parallel to conditions in malaria. Though it is clear much 

 has still to be done in foUowiug out details, there can be no question that in the main the mystery surrounding 

 the passage of piroplasma through the tick has been solved. 



The paper is very well illustrated and the bibliography is very full. In a later 

 article'' he says : — 



Stated briefly, the hereditary cycle of Firoplnsmn is as follows : — 



A parasite in the gut of the adult tick enlarges and becomes a motile, club-shaped body, which then leaves 

 the gut and penetrates an ovum, becoming in the substance of this a zygote. The zygote increases in size and 

 breaks up into sporoblasts, which are found disseminated in the tissues of the larva. In the glands of the nymphs 

 immature sporozoits have collected. In the glands of the adult are found mature sporozoits. 



Development in the nymph to adult infection is identical. Club-shaped bodies are formed in the gut. They 

 leave this, penetrate the tissues, embedding themselves in cells and becoming zygotes. Owing to the growth of 

 the embryonic tissue, the sporoblasts into which the zygote breaks up tend to become disseminated among the 

 cells. Many of these invaded cells later form the salivary gland — a structure which occupies a large portion of 

 the body of the infected tick. The sporozoits thus find themselves in situ. Many parasites, however, invade 

 embryonic cells which do not eventually become salivary tissue, and the sporozoits then probably reach the gland 

 by their own movements. 



' Koch, B. (1906), " Beitr.igo ziir Entwicklungsgesehichte der Piroplasmen." Zcils. f. Hyg. und Infekts. 

 Bd. LIV., No. 1. 



^ Kleine, P. K. (1906), " Kultivierungs versuch der Hunde Piroplasmen." Ibid. 



" Christophers, S. R. (1907), " Piroplasma Canis and its Life Cycle in the Tick." Scientific Memoirs of the 

 Oovernincnt of India, No. 29. 



•* Christophers, S. R. (November 9th, 1907), " Development of Piroplasma Canis in the Tick." British 

 Medical Journal, Vol. II. 



