418 EDGAR H, NORRIS 



stained with alum-haematoxylin and eosin, or iron-haematoxy- 

 lin and eosin. 



Besides the specimens mounted in the collection, other glands 

 from newborn children and from children in the early years of 

 life were obtained at autopsy. These were used merely for pur- 

 poses of comparison, and have neither been listed below, nor 

 discussed in this paper. 



The following table shows the materials used in this work. 

 The embryos and fetuses used are arranged in the order of their 

 crown-rump lengths. 'Minn. E. C refers to the Minnesota 

 Embryological Collection. An asterisk (*) following the num- 

 ber signifies that the thyroid gland alone was sectioned. Other- 

 wise the entire embryo was available in serial sections. 



The ordinary reconstruction methods, both plastic (Born's 

 wax-plate method) and graphic, were utilized in the present 

 study. In all cases where a determination of the follicular form 

 or structure was attempted, special precautions were observed 

 in making the reconstructions as accurate as possible. 



The drawings for reconstruction were made with the camera 

 lucida on transparent paper. After the drawings were com- 

 pleted, those of successive sections were superimposed upon a 

 tracing-table, and each epithehal structm-e in the section given 

 a letter or number. The drawings were controlled by careful 

 microscopic observations, to determine the frequently compli- 

 cated relations of neighboring folUcles. By this method it was 

 possible to determine with certainty what the limits of any par- 

 ticular mass or folhcle might be. 



