446 J. A. BADERTSCHER 



Large lymph ocytes^ are found scattered here and there through- 

 out the mesenchyme of the neck and upper thoracic regions which 

 were the only regions examined. They are characterized by 

 a wide rim of basophilic, nongranular cytoplasm and a large 

 nucleus containing a generous amount of chromatin. Their 

 shape varies; some are nearly spherical while others have an 

 irregular outline with one or more projecting pseud opodia. 

 When treated with Hasting's Nocht's blood stain the cytoplasm 

 takes on a distinct bluish hue the deepness of which may vary 

 in different lymphocytes found in a single section, thus indi- 

 cating that some are more basophilic than others. The rela- 

 tion of faintly stained to the more deeply stained cells will be 

 considered later on in this paper. The nucleus is sharply de- 

 fined from the cytoplasm by a distinct nuclear membrane. The 

 chromatin is in the form of irregular and deeply stained gran- 

 ules which vary much in size. Some of the granules adhere 

 to the nuclear membrane, while others are scattered in the less 

 deeply stained nucleoplasm. In most nuclei only one nucleolus 

 is present but some contain two. The shape of the nucleus 

 often conforms to the shape of the cell body. In round lym- 

 phocytes it usually is round while in the irregular shaped lym- 

 phocytes it may also be irregular in shape. It is impossible 

 to mistake an irregularly shaped lymphocyte with its blue 

 stained cytoplasm and its nucleus rich in chromatin for a spindle 

 or stellate shaped mesenchjnnal cell with slightly reticulated 

 and lightly red stained cytoplasm and a nucleus containing 

 considerably less chromatin. 



While the lymphocytes are scattered singly throughout the 

 entire mesenchyme, local accumulations are also found. These 

 are most pronounced in the upper thoracic region near the large 

 blood vessels and the thoracic segments of the thymus. Most 

 profound growth activity is apparent in the mesenchyme sur- 

 rounding the thoracic segments and it is here that transition 

 stages from mesenchymal cells to lymphocytes frequently 

 occur. Large lymphocytes are quite numerous. Even with 



^ The 'Wanderzellen' of Maximow and other investigators are regarded as being 

 identical to the large lymphocytes. 



