PARASITES OF ACTINOMYCOSIS 657 



ally ; in the latter case masses of growth due to the parasite are found post 

 mortem in the peritoneum, omentum and mesentery. 



2. Morphology. Detection of the parasite. 



A. Microscopical appearance. 



1. In the tissues. -In cases of actinomycosis the pus, sputum, or other in- 

 fected tissues contain sulphur coloured or occasionally whitish opaque grains, 

 varying in size from a lycopodium spore to a millet seed. It is these grains 

 which must be searched for and examined in a suspected case of actinomycosis, 

 and it is very important that the pus or other material should be quite fresh, 

 as the parasite rapidly degenerates. If the grains be scarce and very small it 

 is best to spread a little of the pus in a thin layer on a slide, in this way the 

 grains can easily be seen and collected for further investigation. 



If one of the grains be crushed between a slide and cover-glass in a drop of 

 glycerin the parasite can be readily and easily recognized (fig. 307). When 



FIG. 307. An actinomycosis grain. Unstained FIG. 308. Section through an actino- 



preparation obtained by crushing between two mycotic tubercle. Gram's method. (Oc. 

 slides. II, obj. 8, Heich.) 



crushed in this way the grain will be seen to consist of small mulberry-like 

 bodies composed of a central mass of filaments closely fitted together with 

 numerous diverging rays (a/cn's =a ray) in many cases club-shaped at the 

 free end (yellow colonies, clubs, cross-forms) (vide infra). 



The central part consists of a tangled mass of filaments which appear to be 

 branched, mixed with small swollen corpuscles : here and there a few filaments 

 will be seen to project from the centre and end externally by the side of the 

 clubs : the filaments measure on an average 10-12/x long, the clubs 20-30^ 

 long by 8-10/x broad. The clubs are merely degenerated forms of the parasite, 

 the result of the cellular reaction of the tissues ; the wall of the filament 

 enlarges at the end, thus giving origin to a swelling or club, in the centre 

 of which the original filament can be recognized. Clubs are at first oval in 

 shape, but later degenerate and assume an irregular outline and frequently 

 undergo calcareous degeneration. Clubs are not present in earJy lesions, 

 and only occur when the tissues of the host are markedly resistant ; often 

 indeed when the lesions caused by the parasite are healing the filaments 

 disappear, and only clubs are found. 



In the tissues there is an accumulation around the parasite of epithelioid 

 cells with large oval nuclei. These cells are arranged in a circle and may fuse 

 to form a giant cell containing in addition to several nuclei the parasite itself. 



Staining reactions. The filaments of Discomyces bovis stain with the basic 

 aniline dyes as well as by Gram's and Ziehl's methods, but they are not as 



2T 



