RETICULAR MATERIAL IN THYROID CELLS ol 
bichromate, and mercuric chloride, as reeommended by Bensley 
(10, p. 192), brings to hight, in most tissues, a system of clear 
eanals which bear a very close resemblance in shape and posi- 
tion to the blackened networks (compare figs. 5 and 1); thus there 
are in reality three methods, two positive and one negative, 
which yield the same results. 
We infer that this unknown reticular material is of considerable 
physiologic importance in the living cell; because our methods 
show that the blackened networks (or clear canals) are very 
widely distributed in animal cells and that, in some cases, they 
undergo characteristic and progressive alterations during develop- 
ment and in different physiologic and pathologic conditions. 
We also infer that the reticular material is fluid in consistency 
because there is no indication of the existence of a rigid frame- 
work-in follicular cells teased out in salt solution, and the dis- 
tribution andmovement of cytoplasmic granules, like mitochondria 
do not seem to be restricted. Centrifuging fragments of thyroid 
for upwards of forty-five minutes at 3,500 revolutions per minute 
does not displace it, so that its specific gravity cannot differ 
greatly from the remainder of the cytoplasm. Further evidence 
regarding its fluidity I have presented elsewhere (’21, p. 7). 
It has been suggested that in other glands, like the pancreas, 
the reticular material plays a definite part in secretion. Saguchi 
(20, p. 393) is willing to go so far as to say that ‘“‘the intracellular 
network consists of secreting material which is to be extruded 
either directly into the lumen or indirectly into the intercellular 
eapillary.”’ This is difficult to deny in the thyroid or elsewhere 
because the entire cytoplasm, to say nothing of the nucleus, is 
either directly or indirectly involved. If our inference regarding 
its fluidity iscorrect, many chemical reactions of diverse character 
may take place in it and along its changing surfaces. It is prob- 
ably quite heterogeneous in composition and one of the most 
active areas of the cytoplasm. 
THE AMERICAN JOURNAL OF ANATOMY, VOL, 30, NO. 1 
