758 THE SARCOSPORIDIA 



be again thin and structureless. The parasite then bursts its capsules, the 

 sporozoites are set free and a further infection of the host takes place. 



Infection of new hosts appears to be effected by the curved, non-motile, 

 sausage-shaped sporozoites described by Laveran and Mesnil. These sporo- 

 zoi'tes have rounded ends, of which one is larger than the other and contains 

 a large nucleus surrounded by chromatin granules ; the other end is some- 

 what more pointed [and contains a striated body which may be the analogue 

 of the polar capsule of the Myxosporidia (Guiart)]. The sporozoites are very 

 fragile and can be readily dissociated by keeping them in a moist chamber 

 or by treating them with very dilute acids or alkalis. They probably do not 

 represent the form which the parasite assumes outside the body (Laveran 

 and Mesnil). 



Principal species of Sarcocystis : 



Sarcocystis muris, found in mice and rats. 



Sarcocystis miescheriana, a parasite of pigs, but does not seem to have been found 

 in man. 



Sarcocystis tenella, a common parasite of sheep and goats : this parasite has been 

 found in man (ante). It would appear to be related to Balbiania gigantea, found in 

 the oesophagus of sheep, and apparently a giant form of S. tenella. 



Sarcocystis immitis, found by Kartulis in multiple abscesses of the liver and 

 muscles of a Soudanese. 



Balbiania mucosa, found by Blanchard in the kangaroo and in the connective tissues 

 of a Soudanese, and Balbiania siamensis, a parasite of Siamese buffaloes, are very 

 closely allied to B. gigantea and are therefore included in the genus Sarcocystis. 



Sarcocystis blanchardi, a parasite of European and Javanese buffaloes. 



Toxin. Pfeiffer found that an aqueous extract of Sarcosporidia inoculated 

 beneath the skin of a rabbit led to a fall of temperature, diarrhoea, and ulti- 

 mately to the death of the animal. Laveran and Mesnil repeated Pfeiffer's 

 experiments and proved the existence in the Sarcosporidium of sheep (S. 

 tenella) of a toxin to which they have given the name sarcocystine. Laveran 

 and Mesnil prepared both aqueous and glycerin extracts of Sarcosporidia ; 

 the aqueous extract was found to lose its toxicity rapidly, so that in 6 days 

 it was already much less toxic than when prepared ; the glycerin extract, 

 on the other hand, which is quite as toxic as the aqueous extract, keeps much 

 better and preserves its toxicity unaltered for about a month. 



Preparation of the toxin. Enucleate a number of Sarcosporidia from the oesophagus 

 of a sheep and after weighing them, crush them up in a mortar with sterile sand and 

 a known volume of water or glycerin (according as to whether an aqueous or glycerin 

 extract is to be prepared) : filter the aqueous extract through a porcelain bougie 

 and the glycerin extract through paper. 



If Sarcosporidia be opened and inserted beneath the skin they give rise to 

 the same symptoms as the extracts, but if the cuticle be intact symptoms of 

 intoxication are delayed. Laveran and Mesnil also prepared a highly toxic 

 dry extract. 



Preparation of dry extract. A number of Sarcosporidia are dried in a desiccator 

 over sulphuric acid and powdered ; the white powder constitutes the extract and 

 must be stored in small sealed tubes. One eg. of the dry extract is equivalent to 

 5 or 6 eg. of fresh Sarcosporidia. 



Action on the lower animals. While very toxic for rabbits Sarcocystine is 

 almost without effect on other animals. 



On rabbits. A weight of extract equivalent to 1 mg. of fresh Sarcosporidia inocu- 

 lated beneath the skin of a rabbit weighing 1 kg. leads in about 2 or 3 hours to an 

 attack of diarrhoea accompanied by a fall of temperature to below normal : the 

 cholera-like symptoms become rapidly more marked, convulsions set in and death 

 occurs in about 5-10 hours. Smaller doses of toxin give rise to a slight oedema at 

 the site of inoculation, rise of temperature, and wasting ; diarrhoea is a late symptom 



