THE SYMPATHETIC SYSTEM OF NERVES. 551 



stages of development, may be observed, though certainly not 

 with equal frequency in all individuals, in the Frog. Moreover, 

 in the ganglia of the Mammals I have investigated, there are 

 evidences enough to show that active processes of development 

 are taking place in them, as, for example, the extraordinarily 

 various size of the nerve corpuscles and of the nuclei, the 

 presence of diffuse, finely granular masses with numerous dis- 

 persed lustrous corpuscles, the serially arranged cells without 

 processes, etc. I intend to discuss these points in more detail 

 elsewhere. In investigations made upon the sympathetic of 

 the Frog, the attention of the observer is especially attracted 

 to clusters of small corpuscles composed of nuclei, with small 

 surrounding area of protoplasm, invested by a capsule of con- 

 nective tissue. These cell clusters are aggregated together in 

 variable numbers, and are again enclosed in a common capsule 

 composed of connective tissue, which is in many instances 

 nucleated. The formations just described stand in connection 

 with nerve trunks, and are met with in very variable numbers 

 in different individuals. 



Fig. 268. 



Fig. 268. Cell-cluster. 



The fibres of the sympathetic proceed in part from the 

 cerebro-spinal organ, and partly arise from the sympathetic 

 nerve cells. In the rami communic antes, fibres run both from 

 the spinal cord and the spinal ganglia towards the sympathetic 

 system, and also in the inverse direction. These last fibres 

 may either continue their course in the spinal cord, further 

 towards the centre, or may join the tract of spinal nerves, and 

 run towards the periphery of the body. According to Courvoi- 

 sier, in the animals he examined, including the Pigeon, Rabbit, 

 and Frog, the rami communicantes spread themselves in equal 

 proportions both upwards and downwards in the principal 



