698 



MEDICAL MYCOLOGY 



ment may become branched several times, the whole apparatus as well as its 

 insertion on the axial filament being characterized by an absence of septa. 

 Sporulation, instead of beginning- in any individual helix as soon as it is formed, 

 is usually delayed until the branching and growth of helical hyphae in the 

 same lateral process have come to an end, when it will often proceed rapidly 

 and almost simultaneously in all the helices. The termination of the axial 

 filament itself develojDS into a helix and behaves essentially like a primary 

 lateral branch. 



Occasionally, the axis of one of these racemose arrangements may be 

 comparatively short, resulting in a rather intricate structure where one lateral 

 branch may be entangled with another. The tendencies characteristic of the 

 type, namely, the absence of a septum above the insertion of branches, and 



Fig. 113. — Actinomyces XVIII. Portion of fructification bearing aberrant fertile branches with- 

 out spiral terminations (X2,750). (After Drechsler 1919.) 



the delay in sporulation in the helices first formed, are maintained, however, 

 until the growth of the last order of sporogenous branches is more or less 

 complete. 



Besides species in which these two types are distinct, there are a large 

 number of species in which there is a combination of these two methods. 

 Frequently the open racemose arrangement of the lateral branches on the 

 main axial filament is associated with a successive order of development in 

 the further ramification. The presence of a septum above the insertion of a 

 branch is characteristic of more species than is its absence, and in some species 

 both conditions prevail. 



In a few species there are formed, besides the more regular fructifications, 

 others with relatively thick branching axial hyphae which are densely filled 

 with protoplasm and bear, at very close and irregular intervals, a short thick 



