k 



ACTINOMYCETEAE 695 



may give rise to other branches by lateral proliferation. If these prolifera- 

 tions start close to the tip so that it is difficult to decide which is the main 

 axis, the branching is said to be dichotomous. 



The branches forming the periphery of the actively growing pellicle or 

 the voiino: sporogenons branches attached at intervals to the superficial 

 mycelium, are filled with a dense protoplasm which takes a deep homogeneous 

 stain with hematoxylin. Nearer the origin of the hyphae the contents appear 

 vacuolate. When the vacuoles are excessively large and extend throughout 

 most of the cross-section of the cell, the cytoplasm is confined largely to the 

 walls, leading some of the earlier writers to refer to the Aussenplasma and 

 the Innenplasma. The presence of large vacuoles is often associated with 

 local distentions of the hyphal wall, each swollen segment being largely oc- 

 cupied by a single ellipsoid vacuole, separated from the vacuole of the neigh- 

 boring distention by a protoplasmic partition at the constriction. In other 

 species and in the nutritive mycelium generally there is no marked regularity 

 in the alternation of inflated portions and constrictions, but pronounced devia- 

 tions in the diameter of the filaments may occur with more or less variable 

 frequency. 



Much importance has been attributed by earlier writers to a variety of 

 abnormalities and products of degenerative changes occurring in the myce- 

 lium. In the publications of Israel (1878), Johne and MacFadyean (1889), 

 bodies described as micrococci, cocci, etc., were given minute attention and 

 assigned an important role in the complex ontogeny ascribed to the parasite, 

 supposed to be a pleomorphic bacterium. Wolff and Israel (1891) confused 

 them with the spores of other authors, and as the structures did not have the 

 heat resistance of bacterial spores, they questioned the formation of true spores 

 by Actinomyces. Since they figure only sterile mycelium, it is probable that 

 they were correct in their observations. Bostroem, on the other hand, had 

 both true spores and endogenous granules, which he indiscriminately referred 

 to as spores. 



Round granules, deeply stained in the living filament by very dilute 

 methylene blue, are variable in size and have a method of multiplication and 

 orientation related to the regions of growth in the mycelium. These were 

 called nuclei by Neukirch. Schiitze, using Neukirch's methods, designated 

 them as metachromatic granules. This material is easily distinguished by its 

 powerful affinity for most of the ordinary laboratory stains. In material fixed 

 in alcohol and stained with Delafield's hematoxylin, these granules retain the 

 stain after it has been washed from all other portions of the cell. These 

 granules are rare in the regions of active growth, but in the vacuolated por- 

 tions they are found as minute bodies widely separated from one another. 

 Farther from the tip of the hypha the granules increase in size and frequency, 

 and their arrangement becomes more regular. The individual spherical bodies 

 are nearly equal in size, exactly filling the lumen of the hypha, and are 

 separated by nearly equal spaces. In other cases, the granules seem to coalesce 



