230 The Development of the iN'euroglia 



" neuroglia cells/"' but consists rather of an early formed protoplasmic 

 continuum, or syncytium, extending throughout the confines of the cen- 

 tral nervous system and in which the nuclei are situated at irregular 

 intervals and in irregular numbers; (3) that the later formed appear- 

 ances of the tissue, usually described as " neuroglia cells," are simply 

 masses of this syncytium more or less isolated by being molded into the 

 interspaces resulting from the ingrowth and enlargement of the nervous 

 elements, the " processes of the cells " being only the more attenuated por- 

 tions of the syncytium connecting contiguous larger masses occupying 

 larger interspaces; (3) that finally the neuroglia fibers, or that form of 

 the mature neuroglia which is differentiated by the special neuroglia 

 stains, result from a transformation of the syncytial substance. The fibers 

 in the adult are of irregular and indefinite length. A single fiber may 

 frequently be traced through the domain of several " neuroglia cells." 



These impressions were obtained chiefly from favorable preparations 

 of the adult tissue. To observe the processes by which the neuroglia 

 arises and its fibers develop, the study must of necessity deal with differ- 

 ent stages of the growth and development of the organ containing it. 

 This paper is an attempt to describe certain of these processes thought to 

 be indicated by conditions found in the developing material. 



In general, the literature touching the subject is unsatisfactory, from 

 the fact that in most cases the authors deal with other than the special 

 features herein concerned. Often an author's statements, and his illus- 

 trations especially, show that he has seen certain of the features I shall 

 try to describe, but usually giving special attention to the developing 

 nervous structures, he either leaves the supporting tissue unnoticed or 

 describes its appearance from a different point of view. In fact, the 

 idea of a syncytium in these phases of development seems to be compara- 

 tively new in the literature. 



In order to avoid possible confusion in its use, it is perhaps best to 

 define how the term syncytium is used in this paper : Wherever there 

 occurs a division of the nuclei without a corresponding division of the 

 cytoplasm there results a syncytium, or a condition in which the nuclei 

 are distributed in a common mass of cytoplasm. The nuclei may or 

 may not exhibit a regular form of arrangement; the mass itself may or 

 may not have definite shape. This definition may be strained to include 

 the giant marrow cell or the striated muscle fiber. In these there is a 

 more or less definite shape with a more or less definite arrangement of 

 the nuclei. The periblast of certain early embr3^os has neither. Mall, 

 02, especially describes the early form of the connective tissues of the 

 body as that of a syncytium which results from the fusion of the mesen- 



