472 SPECIAL HISTOLOGY. 



with elongated interstices, which invests the fasciculus, and, 

 in fact, penetrates between its elements ; never, however, sur- 

 rounding individual primitive fibres, but only entire divisions 

 of them. The ganglia contain a delicate capillary plexus, in 

 the form of a network, so that each nerve-cell is surrounded by 

 special vessels. The Pacinian bodies also contain vessels, which 

 even penetrate as far as the central cavity (Todd and Bowman, 

 II, p. 397, fig. 75, and p. 399, fig. 76- Herbst, Tab. IV, 

 figs. 1 and 2). 



[On the subject of the condition of the cutaneous nerves of 

 animals, I would here add a few remarks. In the skin of the tail 

 of batrachian larvae (Rana, Bvfo, Triton, Bombinator, Alytes), 

 I have described the very delicate ramifications and plexuses 

 of the embryonic pale nerve-fibres ; and moreover, quite evident 

 loops of the fully formed dark nerve-tubes, and isolated divisions 

 of the latter (' Ann. des S. Nat./ 1846, p. 102, pi. 6, 7). In 

 the full-grown Frog, according to Czermak (Mull. 'Archiv/ 

 1849, p. 252), the nerves destined to the skin, form, on its 

 inner aspect, a wide network, already described by Burdach, 

 from which again numerous fasciculi are given off, penetrate 

 the derma perpendicularly, and, having reached the superficial 

 glandular layer of the skin, form a superficial nervous- 

 plexus between the glands. With respect to the true ter- 

 mination of the nerve-fibres, Czermak arrived at no definite 

 results, but made the interesting discovery that thick and thin 

 nerve-fibres of the deeper plexus divide dichotomously very fre- 

 quently and repeatedly, and thus spread themselves over larger 

 surfaces ; of which divisions I have most fully satisfied myself 

 from preparations furnished by Czermak. Similar conditions 

 were found by Leydig (' Zeitsch. f. wissen. Zool.,' Ill) in the 

 skin of Fishes ; where also exist superficial and deeper plexuses, 

 with numerous divisions of finer and thicker tubes, all of which 

 on the surface ultimately become quite fine, pale, and finally 

 invisible. In the Invertebrata, as appears from Leydig's re- 

 searches in Argulus, and especially in Carinaria, conditions are 

 met with perfectly analogous to those described by me in the 

 nerves of the Tadpole ; and I cannot agree with Leydig, when 

 he describes the nucleated enlargements as nerve-cells. On 

 the other hand, the conditions observed in Artemia and ( 'orethra 



