114 E. R, HOSKINS AND M. M. HOSKINS 



the dye detectable in this organ is too small to be of practical 

 importance. 



b. Kjdney. Microscopically, the dye can be seen in only a 

 few leucocytes and endothelial cells of the capillaries. 



c. Liver. The liver contains most of the fixed trypan blue in 

 the entire body. This organ is relatively large and in almost 

 every cell in a large number of sections examined there are from 

 five to twenty blue granules of different sizes (fig. 2). In places 

 the granules appear to be in vacuoles. A rather large number of 

 endothelial cells of the sinusoids likewise are seen to contain the 

 dye. In figure 2 one such is seen nearly separated from the wall 

 of the vessel and so full of stain that the nucleus is barely visible. 

 In the liver of the dogfish there is a relatively large amount of 

 normal pigment both in the sinusoids and in the parenchyma, 

 collected into large masses. These black granules are often 

 found in phagocytes. The large mass shown in a sinusoid in 

 figure 2 is made up both of this black pigment and trypan blue 

 granules. These black pigment masses may be found in the 

 bile normally, and in the present experiment both black masses 

 and masses of both blue and black granules were seen. There 

 were found also in the bile many blue granules free and in es- 

 caped cells which are present also in normal bile. All the 

 granules shown in figure 2 in the hepatic and endothelial cells 

 and in the leucocyte are trypan blue. The mass at x is mostly 

 normal black pigment. 



d. Spleen. A free-hand section of the spleen showed the dye 

 to be scattered uniformly through the tissue. The specimen 

 was not examined microscopically, but nearly every cell must 

 have ingested the dye.- 



e. The spiral valve, stomach, post valvular portion of the 

 intestine, muscles, and skin were still light blue in color after 

 being embedded in paraffin, but under the microscope definite 

 blue granules can be seen in only a few free phagocytes in the 

 blood-vessels. A free-hand tangential section of the integument 

 was cleared in oil, but the dye present was too diffuse to be made 

 out after clearing. The pigment in the melanophores was all 

 black and the subcutaneous vessels were colorless. 



