298 J. JACKSON CLARKE. 



observed as associated with the presence of the tubes, and may 

 "with some probability be referred to this cause." ^ 



L. Pfeiffer has demonstrated the nature of these fatal cases, 

 showing that they are the result of the escape of the sickles 

 from the muscle-fibre in which they are developed, and their 

 entrance into the surrounding muscle-fibres, in which they 

 appear as groups of minute round cells, and growing to a 

 certain size constitute a newMiescher's tube, which, unless the 

 host acquires a greater resisting power, again ruptures and 

 liberates its swarm-spores. 



I have been able, both in Dr. Pfeiffer's preparations and in 

 others of my own, to confirm these observations. Pfeiffer has 

 further shown that an emulsion of Sarcosporidia injected into 

 rabbits causes an intense inflammatory reaction and toxic 

 phenomena, and this is in keeping with what is seen in the 

 progressive infection of muscle referred to above. The free 

 spores seem to have a marked attraction for leucocytes (che- 

 miotaxis), and thus the process has been termed by Pfeiffer 

 " myositis sarcosporidica.^^ 



When this progressive infection is limited to a certain region, 

 instead of inflammatory changes tumour formation is seen. 

 Thus in horses L. Pfeiffer has found that tumours included 

 by Kolliker in a group termed " Muskelknospen ^^ are 

 determined by sarcosporidia. Some of Dr. Pfeiffer's 

 sections show this in, I think, a most conclusive manner. 

 The growth possesses a stroma of fibro-cellular tissue, in 

 which three zones may be described : an inner containing 

 dense foci of degenerated material surrounded by giant-cells, 

 &c. ; a middle zone containing numerous Meischer's tubes, 

 from which the sickle-spores are escaping ; and an outer zone 

 containing many muscle-fibres infected by Sarcosporidia. 



One effect of a chronic progressive infection by Sarcosporidia 

 has been most exquisitely shown by the same observer. On 

 the oesophagus of sheep, white cysts, of which the largest are 

 as big as horse-beans, are sometimes encountered. The larger 

 (older) cysts are provided with a fibrous capsule. Dr. Pfeiffer's 



* Leuckart, Hoyle's (1886) translation, p. 202. 



