ACTINOMYCOSIS. 257 



they vary much in length, and are usually quite simple, " but 

 some carried lateral buds, and occasionally two appear to be 

 carried by a common stalk." These buds are best stained by 

 the Ziehl-Neelsen method ; sonie of them exhibit a very 

 important relation to the leptothrix forms already described, 

 the thread appearing to be continued into the centre of 

 the club, the outer part of which is formed by a homo- 

 geneous, somewhat faintly stained material. This axial 

 thread may be divided into longer or shorter segments, 

 corresponding apparently to the bacilli and cocci forms. 

 They are usually most divided and are undergoing most 

 marked changes in the larger clubs, whilst there are also 

 small rounded bodies, which appear to be essentially of the 

 nature of cocci, surrounded by the same material that forms 

 the thickened club. In some of the smaller colonies of the 

 actinomyces Professor M'Fadyean describes cocci only, which 

 are usually arranged in short chains or in little groups. 

 They are embedded in masses of leucocytes, some being 

 actually within the cells, and appearing to be the points 

 from which the larger colonies start, the cocci being carried 

 by the leucocytes from point to point. Other colonies 

 contain only cocci and thread forms, the threads in this case 

 appearing to be developed from cocci, whilst those colonies 

 in which clubs are present appear to be in a still more 

 advanced stage of development. 



By some observers the club-like forms have been described 

 as the spore-bearing parts of the organism, and are spoken of 

 as Conidia. or Basidia, but it appears from the above case, 

 and from those that have been described in the human 

 subject, that the thickened extremity is due merely to a 

 kind of involution process, and occurs in the older thread- 

 like organisms as the result of a growth and swelling 

 of the outer sheath of the Cladothrix threads, this sheath 

 corresponding, in fact, to the gelatinous material which is 

 formed in zooglcea masses of other organisms, or to the 

 capsule first described by Friedlander which is formed around 

 the bacillus of pneumonia. When these clubs are once de- 

 veloped the central part may be only partially active, whilst 

 the periphery remains passive, but extremely resistant to the 

 attacks of the surrounding cells, which attack the club- 

 shaped masses very vigorously, the large thickened clubs 

 being frequently found in various stages of degeneration 



i8 



