3H 



HISTOLOGY 



dermal tissue, and they, as well as the chromaffine cells, are sometimes 

 found in widely different positions. The presence of bodies that cor- 

 respond to renal bodies has been suspected in some invertebrates. This 

 fact is far from being demonstrated, however, and the first of a very 

 interesting taxonomic series of these tissues that we shall study are the 

 renal bodies of an elasmobranch fish, Raja maculata. Both kinds of 

 renal tissue, chromaffine and cortical, are found here, the former as a 

 double row of bodies, one row on the ventral median edge of each kidney. 

 They are larger toward the head, where they form the "axillary hearts." 

 All the parts of these bodies are in intimate contact with branches of the 

 large dorsal blood vessels. 



A section of the anterior "axillary heart" shows that it is a body com- 

 posed of both sympathetic nerve cells and the characteristic chromaffine 



FIG. 282. A, part of a section of a paired adrenal body from the skate, Raja clavata; B, part 

 of a section of the interrenal body from the same fish. (After SWALE VINCENT.) X 450. 



cells. These latter form the greater part of the posterior and internal 

 part of the " gland." They are massed around a blood vessel as a zone 

 of large irregular and branching cells which vary much in size. At the 

 surface they show an irregular columnar arrangement due to their posi- 

 tion. Figure 282, A, represents them taken in the center of the mass. 



The posterior bodies of the two are much the same, except that the 

 farther caudad they are found, the less becomes the nerve-cell portion. 

 In the posterior third of the row the bodies are composed chiefly of 

 chromaffine cells. 



Besides these two rows of paraganglia there may be found another 

 glandular mass without any duct between the two kidneys near their 

 posterior end. Sections of this material (Fig. 282, B} show that it is 

 made up of cortex cells which appear in cords and masses that lie in a 

 sinusoidal plexus of blood vessels. The cords and masses are usually 

 two cells deep, so that each cell has a proximal end in contact with the 



