756 THE SARCOSPORIDIA 



one individual to another. Spore formation represents the sexual (sporogonic) 

 method of reproduction. 



According to Doflein and Laveran multiplication of the Myxosporidia 

 within the host takes place by division into two (equal or unequal) parts 

 (schizogony). The investigations of Thelohan and Hofer on the Myxosporidia 

 of fish and those of Laveran on Myxidium danilewskyi (a parasite of Cistudo 

 europcea) tend to prove that infection takes place via the alimentary canal. 



Of the numerous Myxosporidia which have been described in cold-blooded verte- 

 brates the following may be mentioned : Myxidium danilewskyi, studied by Laveran 

 in a tortoise (Cistudo europcea) : M. Ueberkiihni ; Myxobolus butschli (in fresh- water 

 fish) ; M . cerebralis, described by Hofer as the probable cause of a disease of certain 

 trout ; M . lintoni (in Cyprinodon variegatus) ; M. cyprini which is the cause of 

 " Pockenkrankheit " of carp (Tedeschi) ; Leptofheca agilis (of salt-water fish) ; Cera- 

 tomyxa appendiculata (a parasite of Lophius fiscatorius) ; C. linospora, C. incequcdis 

 (of salt-water fish). 



SECTION III. THE SARCOSPORIDIA. 



The Sarcosporidia are found as parasites in the muscles (striated and non- 

 striated) and sometimes in the connective tissues of the mammalia (mice, 

 rats, monkeys, pigs, cattle, horses, sheep) and birds. 



These protozoa are very seldom found as human parasites. On two occa- 

 sions Sarcocystis tenella, a very common parasite of the sheep, has been found 

 in man and on each occasion by chance -once by Baraban and Saint Remy 

 in the vocal cords of an executed criminal and on the other occasion by Hoche 

 in the muscles of a person who had died of tuberculosis. Kartulis found a 

 sarcosporidium (Sarcocystis immitis) in the liver and muscles of a Soudanese. 

 The parasites found by Hadden, Koch, Klebs and Eve in the kidney, and by 

 Rosenberg in the muscle of the mitral valve of a woman, are [by some] con- 

 sidered to be other instances of sarcosporosis in man. Vuillemin 

 thinks that systematic investigation would show Sarcocystis 

 tenella to be a much more common parasite in man than is 

 generally believed. A sarcosporidium which is parasitic in elks, 

 caribous and deer is also said to be capable of infecting man (H. 

 Brooks). 



The means by which the Sarcosporidia are transmitted from one 

 host to another are still very imperfectly understood but it is 

 probable that infection takes place through the alimentary canal and 

 may be the result of the ingestion of infected meat. Grey mice 

 have been infected by feeding them on the muscles of other mice 

 infected with Sarcosporidia (Smith, Koch) and in these cases there was 

 FIG. 358. a minimum incubation period of 45 days before the parasite appeared 

 m *^ e ti ssues - Negri has infected guinea-pigs by feeding them with 

 (After Laveran Sarcocystis muris. [Kartulis' case (ante) affords some support to the 

 capsu^e^ 31 ^' nu- view that . t . he alimentar y canal is the channel of infection, because 

 cleus surrounded Sarcosporidia were found in small numbers in that situation and they 

 by granules. may quite conceivably have passed through the intestinal wall into 



the branches of the portal vein and so reached the liver (Guiart). ] 

 Morphology. According to Laveran and Mesnil the Sarcosporidia should 

 all be grouped in one genus (Sarcocystis) and in their view there is no sufficient 

 ground for dividing them, as was proposed by Blanchard, into two families 

 according as to whether they are found in the muscles [Miescheria] or connec- 

 tive tissues [Balbiania]. 



These two families were until recently recognized as comprising three genera 

 which were differentiated by the thickness of the enveloping membrane or cuticle 

 of the parasite. The genus Miescheria included intra-muscular species surrounded 



