291 



Notes on the Genus Toxoplasma, with a Description of Three 



New Species. 



By H. G. Plimmer, F.R.S., Professor of Comparative Pathology in the 



The genus Toxoplasma has not yet any definite systematic position. By 

 some, the organisms which bear this name are regarded as being allied to 

 the Leishmania, and by others to the yeasts. This uncertainty must exist 

 so long as we do not know the complete life-history of these organisms ; 

 but, since any addition of new facts concerning them may help towards the 

 acquisition of this knowledge, it has been thought worth while to record 

 the finding of three new varieties, and to describe them. 



The organisms were first seen by Splendore (1), and were described by 

 him in July, 1908. He found them in the blood of a rabbit in Brazil, and 

 the name Toxoplasma was given to them by Nicolle and Manceaux (2), 

 who found them in a gondi in Tunis, shortly after Splendore's discovery, 

 and described them in October, 1908. Since then, others have been found 

 in the dog by Mello in Italy and by Yakimoff in Germany, in the mole by 

 Prowazek in Japan, and in the pigeon by Carini in Brazil. 



It seems probable, so far as our knowledge of these organisms extends at 

 present, that they are more nearly related to the Hremogregarines than to 

 any other of the Hpemosporidia ; they have no micronucleus, and therefore 

 cannot belong to the Leishmania, as Nicolle and Manceaux thought, and 

 the absence of a distinct capsule, and the fact that no budding process has 

 been observed, should prevent them from being regarded as yeasts, as has 

 been suggested. 



The Toxoplasmas may occur free in the blood, but are generally found in 

 the large mononuclear leucocytes ; their distribution in the body of the 

 affected animal is often peculiar. They give rise to very marked wasting 

 and to considerable blood destruction, almost as marked as in the Babesia 

 infections. 



The Toxoplasmas are organisms of either a crescentic or bi-convex shape, 

 sometimes with pointed and sometimes with rounded ends ; occasionally, 

 and under pressure, they may become nearly round. There is no capsule 

 or definite membrane to be seen around them. The protoplasm is very fine 



VOL. LXXXIX. — B. 2 B 



Imperial College of Science and Technology, London., 



(Received February 25, 1916.) 



AUG 281916 



[Plates 9 and 10.] 



