152 HISTOLOGY 



ones pass out of the ganglion, but their terminations are unknown. Small 

 stellate cells, one of which is shown in the figure, presumably belong with 

 the supporting tissue. 



Fibers from the spinal nerves may pass through the sympathetic 

 ganglia, or terminate within them. Thus spinal motor fibers, after 

 losing their myelin sheaths, form pericellular plexuses about the sym- 

 pathetic motor cells, and their collaterals end in the same way. They 

 are apparently indistinguishable from the sympathetic fibers which pass 

 from one ganglion to another and terminate in pericellular networks. 

 Medullated sensory fibers, some of which arise from lamellar corpuscles, 

 extend through the sympathetic nerves to enter the spinal ganglia. 



Chromaffin organs, or paraganglia, are masses or cords of cells which 

 originate in close association with sympathetic ganglia. Although they 

 have often been classed with nervous tissue, they are to be regarded as 

 glands which produce an internal secretion. This secretion acts upon the 

 smooth musculature in the walls of the blood vessels and causes it to 

 maintain a proper state of contraction, or tonus. 



When fresh, chromaffin tissue is darkly colored. If preserved in fluids 

 containing chromic acid or salts of chromium, the cells which contain 

 secretion acquire a yellowish-brown stain. The term chromaffin refers 

 to this specific affinity for chromium, and does not mean that the cells 

 stain deeply. 



Groups of chromaffin cells are found in connection with the ganglionated 

 trunk of the sympathetic system. In the new-born child these "chromaf- 

 fin bodies" may reach a length of 1-1.5 mm. (Zuckerkandl) and several 

 of them may be associated with a single ganglion. They are always found 

 in the plexus at the bifurcation of the carotid artery, where they enter 

 into the formation of the carotid gland (glomus caroticum). They occur 

 in varying numbers in the cceliac, renal and hypogastric plexuses, and extend 

 along the vessels so that chromanin cells are found in relation with the 

 kidneys, ureters, prostate, epididymis and ovary. The largest bodies 

 (the organs of Zuckerkandl) are found on either side of the inferior mesen- 

 teric artery, and may connect with one another by a bridge across the 

 front of the aorta. At birth "the average length of the right one is u.6 

 mm., and of the left, 8.8 mm." Usually there are two chromaffin bodies 

 on either side in the hypogastric plexus, but the total number of bodies 

 connected with the abdominal plexuses varies greatly, "from 7 to 26, or 

 even more; in one case nearly 70" (Zuckerkandl). Although they undergo 

 regressive changes after birth, they do not dissappear. 



The medulla of the suprarenal glands consists of chromaffin tissue, 

 which has very important functions throughout life; it will be described 

 in connection with the suprarenal glands. 



